Sex Chromosomes: The homologous chromosomes that are dissimilar in the heterogametic sex. There are the X CHROMOSOME, the Y CHROMOSOME, and the W, Z chromosomes (in animals in which the female is the heterogametic sex (the silkworm moth Bombyx mori, for example)). In such cases the W chromosome is the female-determining and the male is ZZ. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Chromosomes: In a prokaryotic cell or in the nucleus of a eukaryotic cell, a structure consisting of or containing DNA which carries the genetic information essential to the cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Sex Chromosome Aberrations: Abnormal number or structure of the SEX CHROMOSOMES. Some sex chromosome aberrations are associated with SEX CHROMOSOME DISORDERS and SEX CHROMOSOME DISORDERS OF SEX DEVELOPMENT.Chromosome Mapping: Any method used for determining the location of and relative distances between genes on a chromosome.X Chromosome: The female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in human and other male-heterogametic species.Y Chromosome: The male sex chromosome, being the differential sex chromosome carried by half the male gametes and none of the female gametes in humans and in some other male-heterogametic species in which the homologue of the X chromosome has been retained.Sex Chromosome Disorders: Clinical conditions caused by an abnormal sex chromosome constitution (SEX CHROMOSOME ABERRATIONS), in which there is extra or missing sex chromosome material (either a whole chromosome or a chromosome segment).Chromosome Banding: Staining of bands, or chromosome segments, allowing the precise identification of individual chromosomes or parts of chromosomes. Applications include the determination of chromosome rearrangements in malformation syndromes and cancer, the chemistry of chromosome segments, chromosome changes during evolution, and, in conjunction with cell hybridization studies, chromosome mapping.Chromosomes, Human, X: The human female sex chromosome, being the differential sex chromosome carried by half the male gametes and all female gametes in humans.Chromosome Aberrations: Abnormal number or structure of chromosomes. Chromosome aberrations may result in CHROMOSOME DISORDERS.Chromosomes, Human, Y: The human male sex chromosome, being the differential sex chromosome carried by half the male gametes and none of the female gametes in humans.Sex Determination Processes: The mechanisms by which the SEX of an individual's GONADS are fixed.Chromosome Pairing: The alignment of CHROMOSOMES at homologous sequences.Chromosomes, Plant: Complex nucleoprotein structures which contain the genomic DNA and are part of the CELL NUCLEUS of PLANTS.Silene: A plant genus of the family CARYOPHYLLACEAE. The common name of campion is also used with LYCHNIS. The common name of 'pink' can be confused with other plants.X Chromosome Inactivation: A dosage compensation process occurring at an early embryonic stage in mammalian development whereby, at random, one X CHROMOSOME of the pair is repressed in the somatic cells of females.Chromosome Segregation: The orderly segregation of CHROMOSOMES during MEIOSIS or MITOSIS.In Situ Hybridization, Fluorescence: A type of IN SITU HYBRIDIZATION in which target sequences are stained with fluorescent dye so their location and size can be determined using fluorescence microscopy. This staining is sufficiently distinct that the hybridization signal can be seen both in metaphase spreads and in interphase nuclei.Chromosomes, Human: Very long DNA molecules and associated proteins, HISTONES, and non-histone chromosomal proteins (CHROMOSOMAL PROTEINS, NON-HISTONE). Normally 46 chromosomes, including two sex chromosomes are found in the nucleus of human cells. They carry the hereditary information of the individual.Karyotyping: Mapping of the KARYOTYPE of a cell.Chromosomes, Human, Pair 1: A specific pair of human chromosomes in group A (CHROMOSOMES, HUMAN, 1-3) of the human chromosome classification.Genes, Y-Linked: Genes that are located on the Y CHROMOSOME.Genes, X-Linked: Genes that are located on the X CHROMOSOME.Aneuploidy: The chromosomal constitution of cells which deviate from the normal by the addition or subtraction of CHROMOSOMES, chromosome pairs, or chromosome fragments. In a normally diploid cell (DIPLOIDY) the loss of a chromosome pair is termed nullisomy (symbol: 2N-2), the loss of a single chromosome is MONOSOMY (symbol: 2N-1), the addition of a chromosome pair is tetrasomy (symbol: 2N+2), the addition of a single chromosome is TRISOMY (symbol: 2N+1).Chromosome Painting: A technique for visualizing CHROMOSOME ABERRATIONS using fluorescently labeled DNA probes which are hybridized to chromosomal DNA. Multiple fluorochromes may be attached to the probes. Upon hybridization, this produces a multicolored, or painted, effect with a unique color at each site of hybridization. This technique may also be used to identify cross-species homology by labeling probes from one species for hybridization with chromosomes from another species.Chromosomes, Artificial, Bacterial: DNA constructs that are composed of, at least, a REPLICATION ORIGIN, for successful replication, propagation to and maintenance as an extra chromosome in bacteria. In addition, they can carry large amounts (about 200 kilobases) of other sequence for a variety of bioengineering purposes.Chromosomes, Bacterial: Structures within the nucleus of bacterial cells consisting of or containing DNA, which carry genetic information essential to the cell.Chromosomes, Human, Pair 21: A specific pair of GROUP G CHROMOSOMES of the human chromosome classification.Platypus: A small aquatic oviparous mammal of the order Monotremata found in Australia and Tasmania.Chromosomes, Insect: Structures within the CELL NUCLEUS of insect cells containing DNA.Sex Characteristics: Those characteristics that distinguish one SEX from the other. The primary sex characteristics are the OVARIES and TESTES and their related hormones. Secondary sex characteristics are those which are masculine or feminine but not directly related to reproduction.Meiosis: A type of CELL NUCLEUS division, occurring during maturation of the GERM CELLS. Two successive cell nucleus divisions following a single chromosome duplication (S PHASE) result in daughter cells with half the number of CHROMOSOMES as the parent cells.Chromosomes, Human, Pair 7: A specific pair of GROUP C CHROMOSOMES of the human chromosome classification.Chromosomes, Human, Pair 11: A specific pair of GROUP C CHROMOSOMES of the human chromosome classification.Chromosomes, Human, Pair 17: A specific pair of GROUP E CHROMOSOMES of the human chromosome classification.Sex Chromatin: In the interphase nucleus, a condensed mass of chromatin representing an inactivated X chromosome. Each X CHROMOSOME, in excess of one, forms sex chromatin (Barr body) in the mammalian nucleus. (from King & Stansfield, A Dictionary of Genetics, 4th ed)Chromosome Deletion: Actual loss of portion of a chromosome.Klinefelter Syndrome: A form of male HYPOGONADISM, characterized by the presence of an extra X CHROMOSOME, small TESTES, seminiferous tubule dysgenesis, elevated levels of GONADOTROPINS, low serum TESTOSTERONE, underdeveloped secondary sex characteristics, and male infertility (INFERTILITY, MALE). Patients tend to have long legs and a slim, tall stature. GYNECOMASTIA is present in many of the patients. The classic form has the karyotype 47,XXY. Several karyotype variants include 48,XXYY; 48,XXXY; 49,XXXXY, and mosaic patterns ( 46,XY/47,XXY; 47,XXY/48,XXXY, etc.).Chromosomes, Fungal: Structures within the nucleus of fungal cells consisting of or containing DNA, which carry genetic information essential to the cell.Chromosomes, Human, Pair 6: A specific pair GROUP C CHROMSOMES of the human chromosome classification.Chromosome Disorders: Clinical conditions caused by an abnormal chromosome constitution in which there is extra or missing chromosome material (either a whole chromosome or a chromosome segment). (from Thompson et al., Genetics in Medicine, 5th ed, p429)XYY Karyotype: Abnormal genetic constitution in males characterized by an extra Y chromosome.Chromosomes, Mammalian: Complex nucleoprotein structures which contain the genomic DNA and are part of the CELL NUCLEUS of MAMMALS.Chromosomes, Human, Pair 9: A specific pair of GROUP C CHROMSOMES of the human chromosome classification.Chromosomes, Human, Pair 13: A specific pair of GROUP D CHROMOSOMES of the human chromosome classification.Chromosomes, Human, Pair 18: A specific pair of GROUP E CHROMOSOMES of the human chromosome classification.Spermatocytes: Male germ cells derived from SPERMATOGONIA. The euploid primary spermatocytes undergo MEIOSIS and give rise to the haploid secondary spermatocytes which in turn give rise to SPERMATIDS.Genes, sry: The primary testis-determining gene in mammalians, located on the Y CHROMOSOME. It codes for a high mobility group box transcription factor (TRANSCRIPTION FACTORS) which initiates the development of the TESTES from the embryonic GONADS.Pachytene Stage: The stage in the first meiotic prophase, following ZYGOTENE STAGE, when CROSSING OVER between homologous CHROMOSOMES begins.Chromosome Structures: Structures which are contained in or part of CHROMOSOMES.Chromosomes, Human, 6-12 and X: The medium-sized, submetacentric human chromosomes, called group C in the human chromosome classification. This group consists of chromosome pairs 6, 7, 8, 9, 10, 11, and 12 and the X chromosome.Genetic Linkage: The co-inheritance of two or more non-allelic GENES due to their being located more or less closely on the same CHROMOSOME.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Dosage Compensation, Genetic: Genetic mechanisms that allow GENES to be expressed at a similar level irrespective of their GENE DOSAGE. This term is usually used in discussing genes that lie on the SEX CHROMOSOMES. Because the sex chromosomes are only partially homologous, there is a different copy number, i.e., dosage, of these genes in males vs. females. In DROSOPHILA, dosage compensation is accomplished by hypertranscription of genes located on the X CHROMOSOME. In mammals, dosage compensation of X chromosome genes is accomplished by random X CHROMOSOME INACTIVATION of one of the two X chromosomes in the female.Chromosomes, Human, Pair 2: A specific pair of human chromosomes in group A (CHROMOSOMES, HUMAN, 1-3) of the human chromosome classification.Chromosomes, Human, Pair 16: A specific pair of GROUP E CHROMOSOMES of the human chromosome classification.Chromosomes, Human, Pair 22: A specific pair of GROUP G CHROMOSOMES of the human chromosome classification.Carica: A plant genus of the family Caricaceae, order Violales, subclass Dilleniidae, class Magnoliopsida. It is the source of edible fruit and PAPAIN.Chromosomes, Human, Pair 4: A specific pair of GROUP B CHROMOSOMES of the human chromosome classification.Chromosomes, Human, Pair 10: A specific pair of GROUP C CHROMOSOMES of the human chromosome classification.Chromosomes, Human, Pair 8: A specific pair of GROUP C CHROMOSOMES of the human chromosome classification.Chromosomes, Human, Pair 19: A specific pair of GROUP F CHROMOSOMES of the human chromosome classification.Sex Factors: Maleness or femaleness as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or effect of a circumstance. It is used with human or animal concepts but should be differentiated from SEX CHARACTERISTICS, anatomical or physiological manifestations of sex, and from SEX DISTRIBUTION, the number of males and females in given circumstances.Chromosomes, Human, Pair 20: A specific pair of GROUP F CHROMOSOMES of the human chromosome classification.Sex Differentiation: The process in developing sex- or gender-specific tissue, organ, or function after SEX DETERMINATION PROCESSES have set the sex of the GONADS. Major areas of sex differentiation occur in the reproductive tract (GENITALIA) and the brain.Chromosomes, Human, Pair 12: A specific pair of GROUP C CHROMOSOMES of the human chromosome classification.Chromosomes, Human, 1-3: The large, metacentric human chromosomes, called group A in the human chromosome classification. This group consists of chromosome pairs 1, 2, and 3.Chromosomes, Human, Pair 5: One of the two pairs of human chromosomes in the group B class (CHROMOSOMES, HUMAN, 4-5).Genetic Markers: A phenotypically recognizable genetic trait which can be used to identify a genetic locus, a linkage group, or a recombination event.Chromosomes, Human, Pair 15: A specific pair of GROUP D CHROMOSOMES of the human chromosome classification.Mosaicism: The occurrence in an individual of two or more cell populations of different chromosomal constitutions, derived from a single ZYGOTE, as opposed to CHIMERISM in which the different cell populations are derived from more than one zygote.Chromosomes, Human, 21-22 and Y: The short, acrocentric human chromosomes, called group G in the human chromosome classification. This group consists of chromosome pairs 21 and 22 and the Y chromosome.Recombination, Genetic: Production of new arrangements of DNA by various mechanisms such as assortment and segregation, CROSSING OVER; GENE CONVERSION; GENETIC TRANSFORMATION; GENETIC CONJUGATION; GENETIC TRANSDUCTION; or mixed infection of viruses.Chromosome Inversion: An aberration in which a chromosomal segment is deleted and reinserted in the same place but turned 180 degrees from its original orientation, so that the gene sequence for the segment is reversed with respect to that of the rest of the chromosome.Chromosomes, Human, Pair 14: A specific pair of GROUP D CHROMOSOMES of the human chromosome classification.Chromosomes, Human, 16-18: The short, submetacentric human chromosomes, called group E in the human chromosome classification. This group consists of chromosome pairs 16, 17, and 18.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Chromosomes, Artificial, Yeast: Chromosomes in which fragments of exogenous DNA ranging in length up to several hundred kilobase pairs have been cloned into yeast through ligation to vector sequences. These artificial chromosomes are used extensively in molecular biology for the construction of comprehensive genomic libraries of higher organisms.Chromosomes, Human, 13-15: The medium-sized, acrocentric human chromosomes, called group D in the human chromosome classification. This group consists of chromosome pairs 13, 14, and 15.Crosses, Genetic: Deliberate breeding of two different individuals that results in offspring that carry part of the genetic material of each parent. The parent organisms must be genetically compatible and may be from different varieties or closely related species.Sex Determination Analysis: Validation of the SEX of an individual by inspection of the GONADS and/or by genetic tests.Centromere: The clear constricted portion of the chromosome at which the chromatids are joined and by which the chromosome is attached to the spindle during cell division.Turner Syndrome: A syndrome of defective gonadal development in phenotypic females associated with the karyotype 45,X (or 45,XO). Patients generally are of short stature with undifferentiated GONADS (streak gonads), SEXUAL INFANTILISM, HYPOGONADISM, webbing of the neck, cubitus valgus, elevated GONADOTROPINS, decreased ESTRADIOL level in blood, and CONGENITAL HEART DEFECTS. NOONAN SYNDROME (also called Pseudo-Turner Syndrome and Male Turner Syndrome) resembles this disorder; however, it occurs in males and females with a normal karyotype and is inherited as an autosomal dominant.Chromosome Breakage: A type of chromosomal aberration involving DNA BREAKS. Chromosome breakage can result in CHROMOSOMAL TRANSLOCATION; CHROMOSOME INVERSION; or SEQUENCE DELETION.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Translocation, Genetic: A type of chromosome aberration characterized by CHROMOSOME BREAKAGE and transfer of the broken-off portion to another location, often to a different chromosome.Karyotype: The full set of CHROMOSOMES presented as a systematized array of METAPHASE chromosomes from a photomicrograph of a single CELL NUCLEUS arranged in pairs in descending order of size and according to the position of the CENTROMERE. (From Stedman, 25th ed)Ring Chromosomes: Aberrant chromosomes with no ends, i.e., circular.Disorders of Sex Development: In gonochoristic organisms, congenital conditions in which development of chromosomal, gonadal, or anatomical sex is atypical. Effects from exposure to abnormal levels of GONADAL HORMONES in the maternal environment, or disruption of the function of those hormones by ENDOCRINE DISRUPTORS are included.Models, Genetic: Theoretical representations that simulate the behavior or activity of genetic processes or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Spermatogenesis: The process of germ cell development in the male from the primordial germ cells, through SPERMATOGONIA; SPERMATOCYTES; SPERMATIDS; to the mature haploid SPERMATOZOA.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Trisomy: The possession of a third chromosome of any one type in an otherwise diploid cell.Chromosome Positioning: The mechanisms of eukaryotic CELLS that place or keep the CHROMOSOMES in a particular SUBNUCLEAR SPACE.Nondisjunction, Genetic: The failure of homologous CHROMOSOMES or CHROMATIDS to segregate during MITOSIS or MEIOSIS with the result that one daughter cell has both of a pair of parental chromosomes or chromatids and the other has none.Chromosomes, Human, 4-5: The large, submetacentric human chromosomes, called group B in the human chromosome classification. This group consists of chromosome pairs 4 and 5.Sex Chromosome Disorders of Sex Development: Congenital conditions of atypical sexual development associated with abnormal sex chromosome constitutions including MONOSOMY; TRISOMY; and MOSAICISM.Metaphase: The phase of cell nucleus division following PROMETAPHASE, in which the CHROMOSOMES line up across the equatorial plane of the SPINDLE APPARATUS prior to separation.Spermatozoa: Mature male germ cells derived from SPERMATIDS. As spermatids move toward the lumen of the SEMINIFEROUS TUBULES, they undergo extensive structural changes including the loss of cytoplasm, condensation of CHROMATIN into the SPERM HEAD, formation of the ACROSOME cap, the SPERM MIDPIECE and the SPERM TAIL that provides motility.Microsatellite Repeats: A variety of simple repeat sequences that are distributed throughout the GENOME. They are characterized by a short repeat unit of 2-8 basepairs that is repeated up to 100 times. They are also known as short tandem repeats (STRs).Dromaiidae: A family of flightless, running BIRDS, in the order Casuariiformes. The emu is the only surviving member of the family. They naturally inhabit forests, open plains, and grasslands in Australia.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Marsupialia: An infraclass of MAMMALS, also called Metatheria, where the young are born at an early stage of development and continue to develop in a pouch (marsupium). In contrast to Eutheria (placentals), marsupials have an incomplete PLACENTA.Sex: The totality of characteristics of reproductive structure, functions, PHENOTYPE, and GENOTYPE, differentiating the MALE from the FEMALE organism.Diploidy: The chromosomal constitution of cells, in which each type of CHROMOSOME is represented twice. Symbol: 2N or 2X.Infertility, Male: The inability of the male to effect FERTILIZATION of an OVUM after a specified period of unprotected intercourse. Male sterility is permanent infertility.Mitosis: A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Chromosome Duplication: An aberration in which an extra chromosome or a chromosomal segment is made.Alleles: Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.Hybrid Cells: Any cell, other than a ZYGOTE, that contains elements (such as NUCLEI and CYTOPLASM) from two or more different cells, usually produced by artificial CELL FUSION.Smegmamorpha: Group of fish under the superorder Acanthopterygii, separate from the PERCIFORMES, which includes swamp eels, mullets, sticklebacks, seahorses, spiny eels, rainbowfishes, and KILLIFISHES. The name is derived from the six taxa which comprise the group. (From, 8/4/2000)Chromosomes, Human, 19-20: The short, metacentric human chromosomes, called group F in the human chromosome classification. This group consists of chromosome pairs 19 and 20.Chromosomes, Artificial: DNA constructs that are composed of, at least, elements such as a REPLICATION ORIGIN; TELOMERE; and CENTROMERE, that are required for successful replication, propagation to and maintenance in progeny cells. In addition, they are constructed to carry other sequences for analysis or gene transfer.Prophase: The first phase of cell nucleus division, in which the CHROMOSOMES become visible, the CELL NUCLEUS starts to lose its identity, the SPINDLE APPARATUS appears, and the CENTRIOLES migrate toward opposite poles.Gene Dosage: The number of copies of a given gene present in the cell of an organism. An increase in gene dosage (by GENE DUPLICATION for example) can result in higher levels of gene product formation. GENE DOSAGE COMPENSATION mechanisms result in adjustments to the level GENE EXPRESSION when there are changes or differences in gene dosage.Sex Ratio: The number of males per 100 females.Testis: The male gonad containing two functional parts: the SEMINIFEROUS TUBULES for the production and transport of male germ cells (SPERMATOGENESIS) and the interstitial compartment containing LEYDIG CELLS that produce ANDROGENS.Pedigree: The record of descent or ancestry, particularly of a particular condition or trait, indicating individual family members, their relationships, and their status with respect to the trait or condition.Cytogenetic Analysis: Examination of CHROMOSOMES to diagnose, classify, screen for, or manage genetic diseases and abnormalities. Following preparation of the sample, KARYOTYPING is performed and/or the specific chromosomes are analyzed.Muntjacs: A genus, Muntiacus, of the deer family (Cervidae) comprising six species living in China, Tibet, Nepal, India, the Malay Peninsula, and neighboring island countries. They are usually found in forests and areas of dense vegetation, usually not far from water. They emit a deep barklike sound which gives them the name "barking deer." If they sense a predator they will "bark" for an hour or more. They are hunted for their meat and skins; they thrive in captivity and are found in many zoos. The Indian muntjac is believed to have the lowest chromosome number in mammals and cell lines derived from them figure widely in chromosome and DNA studies. (From Walker's Mammals of the World, 5th ed., p1366)Spermatids: Male germ cells derived from the haploid secondary SPERMATOCYTES. Without further division, spermatids undergo structural changes and give rise to SPERMATOZOA.Characiformes: An order of fresh water fish with 18 families and over 1600 species. The order includes CHARACINS, hatchetfish, piranhas, and TETRAS.Gonadal Dysgenesis, Mixed: A type of defective gonadal development in patients with a wide spectrum of chromosomal mosaic variants. Their karyotypes are of partial sex chromosome monosomy resulting from an absence or an abnormal second sex chromosome (X or Y). Karyotypes include 45,X/46,XX; 45,X/46,XX/47,XXX; 46,XXp-; 45,X/46,XY; 45,X/47,XYY; 46,XYpi; etc. The spectrum of phenotypes may range from phenotypic female to phenotypic male including variations in gonads and internal and external genitalia, depending on the ratio in each gonad of 45,X primordial germ cells to those with normal 46,XX or 46,XY constitution.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Meiotic Prophase I: The prophase of the first division of MEIOSIS (in which homologous CHROMOSOME SEGREGATION occurs). It is divided into five stages: leptonema, zygonema, PACHYNEMA, diplonema, and diakinesis.Drosophila melanogaster: A species of fruit fly much used in genetics because of the large size of its chromosomes.DNA, Satellite: Highly repetitive DNA sequences found in HETEROCHROMATIN, mainly near centromeres. They are composed of simple sequences (very short) (see MINISATELLITE REPEATS) repeated in tandem many times to form large blocks of sequence. Additionally, following the accumulation of mutations, these blocks of repeats have been repeated in tandem themselves. The degree of repetition is on the order of 1000 to 10 million at each locus. Loci are few, usually one or two per chromosome. They were called satellites since in density gradients, they often sediment as distinct, satellite bands separate from the bulk of genomic DNA owing to a distinct BASE COMPOSITION.Lod Score: The total relative probability, expressed on a logarithmic scale, that a linkage relationship exists among selected loci. Lod is an acronym for "logarithmic odds."Sex-Determining Region Y Protein: A transcription factor that plays an essential role in the development of the TESTES. It is encoded by a gene on the Y chromosome and contains a specific HMG-BOX DOMAIN that is found within members of the SOX family of transcription factors.Monosomy: The condition in which one chromosome of a pair is missing. In a normally diploid cell it is represented symbolically as 2N-1.Genetic Variation: Genotypic differences observed among individuals in a population.Diptera: An order of the class Insecta. Wings, when present, number two and distinguish Diptera from other so-called flies, while the halteres, or reduced hindwings, separate Diptera from other insects with one pair of wings. The order includes the families Calliphoridae, Oestridae, Phoridae, SARCOPHAGIDAE, Scatophagidae, Sciaridae, SIMULIIDAE, Tabanidae, Therevidae, Trypetidae, CERATOPOGONIDAE; CHIRONOMIDAE; CULICIDAE; DROSOPHILIDAE; GLOSSINIDAE; MUSCIDAE; TEPHRITIDAE; and PSYCHODIDAE. The larval form of Diptera species are called maggots (see LARVA).DNA Probes: Species- or subspecies-specific DNA (including COMPLEMENTARY DNA; conserved genes, whole chromosomes, or whole genomes) used in hybridization studies in order to identify microorganisms, to measure DNA-DNA homologies, to group subspecies, etc. The DNA probe hybridizes with a specific mRNA, if present. Conventional techniques used for testing for the hybridization product include dot blot assays, Southern blot assays, and DNA:RNA hybrid-specific antibody tests. Conventional labels for the DNA probe include the radioisotope labels 32P and 125I and the chemical label biotin. The use of DNA probes provides a specific, sensitive, rapid, and inexpensive replacement for cell culture techniques for diagnosing infections.Repetitive Sequences, Nucleic Acid: Sequences of DNA or RNA that occur in multiple copies. There are several types: INTERSPERSED REPETITIVE SEQUENCES are copies of transposable elements (DNA TRANSPOSABLE ELEMENTS or RETROELEMENTS) dispersed throughout the genome. TERMINAL REPEAT SEQUENCES flank both ends of another sequence, for example, the long terminal repeats (LTRs) on RETROVIRUSES. Variations may be direct repeats, those occurring in the same direction, or inverted repeats, those opposite to each other in direction. TANDEM REPEAT SEQUENCES are copies which lie adjacent to each other, direct or inverted (INVERTED REPEAT SEQUENCES).DNA: A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Oligospermia: A condition of suboptimal concentration of SPERMATOZOA in the ejaculated SEMEN to ensure successful FERTILIZATION of an OVUM. In humans, oligospermia is defined as a sperm count below 20 million per milliliter semen.Cytogenetics: A subdiscipline of genetics which deals with the cytological and molecular analysis of the CHROMOSOMES, and location of the GENES on chromosomes, and the movements of chromosomes during the CELL CYCLE.Telomere: A terminal section of a chromosome which has a specialized structure and which is involved in chromosomal replication and stability. Its length is believed to be a few hundred base pairs.Nucleic Acid Hybridization: Widely used technique which exploits the ability of complementary sequences in single-stranded DNAs or RNAs to pair with each other to form a double helix. Hybridization can take place between two complimentary DNA sequences, between a single-stranded DNA and a complementary RNA, or between two RNA sequences. The technique is used to detect and isolate specific sequences, measure homology, or define other characteristics of one or both strands. (Kendrew, Encyclopedia of Molecular Biology, 1994, p503)Drosophila: A genus of small, two-winged flies containing approximately 900 described species. These organisms are the most extensively studied of all genera from the standpoint of genetics and cytology.Sex Preselection: Methods for controlling genetic SEX of offspring.Physical Chromosome Mapping: Mapping of the linear order of genes on a chromosome with units indicating their distances by using methods other than genetic recombination. These methods include nucleotide sequencing, overlapping deletions in polytene chromosomes, and electron micrography of heteroduplex DNA. (From King & Stansfield, A Dictionary of Genetics, 5th ed)Genes, Insect: The functional hereditary units of INSECTS.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Chromosomal Proteins, Non-Histone: Nucleoproteins, which in contrast to HISTONES, are acid insoluble. They are involved in chromosomal functions; e.g. they bind selectively to DNA, stimulate transcription resulting in tissue-specific RNA synthesis and undergo specific changes in response to various hormones or phytomitogens.Chromatin: The material of CHROMOSOMES. It is a complex of DNA; HISTONES; and nonhistone proteins (CHROMOSOMAL PROTEINS, NON-HISTONE) found within the nucleus of a cell.Synaptonemal Complex: The three-part structure of ribbon-like proteinaceous material that serves to align and join the paired homologous CHROMOSOMES. It is formed during the ZYGOTENE STAGE of the first meiotic division. It is a prerequisite for CROSSING OVER.Genome: The genetic complement of an organism, including all of its GENES, as represented in its DNA, or in some cases, its RNA.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Echidna: An oviparous burrowing mammal of the order Monotremata native to Australia, Tasmania, and New Guinea. It has hair mingled with spines on the upper part of the body and is adapted for feeding on ants.Haploidy: The chromosomal constitution of cells, in which each type of CHROMOSOME is represented once. Symbol: N.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Birds: Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.Heterozygote: An individual having different alleles at one or more loci regarding a specific character.Haplotypes: The genetic constitution of individuals with respect to one member of a pair of allelic genes, or sets of genes that are closely linked and tend to be inherited together such as those of the MAJOR HISTOCOMPATIBILITY COMPLEX.Mammals: Warm-blooded vertebrate animals belonging to the class Mammalia, including all that possess hair and suckle their young.Blotting, Southern: A method (first developed by E.M. Southern) for detection of DNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.Quantitative Trait Loci: Genetic loci associated with a QUANTITATIVE TRAIT.Fragaria: A plant genus of the family ROSACEAE known for the edible fruit.Didelphis: A genus of large OPOSSUMS in the family Didelphidae, found in the Americas. The species Didelphis virginiana is prominent in North America.Polyploidy: The chromosomal constitution of a cell containing multiples of the normal number of CHROMOSOMES; includes triploidy (symbol: 3N), tetraploidy (symbol: 4N), etc.Hybridization, Genetic: The genetic process of crossbreeding between genetically dissimilar parents to produce a hybrid.Polymorphism, Genetic: The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.Genes: A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms.Nuclear Proteins: Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.Chromosomes, Artificial, Human: DNA constructs that are composed of, at least, all elements, such as a REPLICATION ORIGIN; TELOMERE; and CENTROMERE, required for successful replication, propagation to and maintainance in progeny human cells. In addition, they are constructed to carry other sequences for analysis or gene transfer.Kinetochores: Large multiprotein complexes that bind the centromeres of the chromosomes to the microtubules of the mitotic spindle during metaphase in the cell cycle.LizardsGenetic Loci: Specific regions that are mapped within a GENOME. Genetic loci are usually identified with a shorthand notation that indicates the chromosome number and the position of a specific band along the P or Q arm of the chromosome where they are found. For example the locus 6p21 is found within band 21 of the P-arm of CHROMOSOME 6. Many well known genetic loci are also known by common names that are associated with a genetic function or HEREDITARY DISEASE.Histones: Small chromosomal proteins (approx 12-20 kD) possessing an open, unfolded structure and attached to the DNA in cell nuclei by ionic linkages. Classification into the various types (designated histone I, histone II, etc.) is based on the relative amounts of arginine and lysine in each.Heterochromatin: The portion of chromosome material that remains condensed and is transcriptionally inactive during INTERPHASE.Sequence Homology, Nucleic Acid: The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.Chromosome Walking: A technique with which an unknown region of a chromosome can be explored. It is generally used to isolate a locus of interest for which no probe is available but that is known to be linked to a gene which has been identified and cloned. A fragment containing a known gene is selected and used as a probe to identify other overlapping fragments which contain the same gene. The nucleotide sequences of these fragments can then be characterized. This process continues for the length of the chromosome.Multigene Family: A set of genes descended by duplication and variation from some ancestral gene. Such genes may be clustered together on the same chromosome or dispersed on different chromosomes. Examples of multigene families include those that encode the hemoglobins, immunoglobulins, histocompatibility antigens, actins, tubulins, keratins, collagens, heat shock proteins, salivary glue proteins, chorion proteins, cuticle proteins, yolk proteins, and phaseolins, as well as histones, ribosomal RNA, and transfer RNA genes. The latter three are examples of reiterated genes, where hundreds of identical genes are present in a tandem array. (King & Stanfield, A Dictionary of Genetics, 4th ed)Retroelements: Elements that are transcribed into RNA, reverse-transcribed into DNA and then inserted into a new site in the genome. Long terminal repeats (LTRs) similar to those from retroviruses are contained in retrotransposons and retrovirus-like elements. Retroposons, such as LONG INTERSPERSED NUCLEOTIDE ELEMENTS and SHORT INTERSPERSED NUCLEOTIDE ELEMENTS do not contain LTRs.Genes, Plant: The functional hereditary units of PLANTS.Genes, Mating Type, Fungal: Fungal genes that mostly encode TRANSCRIPTION FACTORS. In some FUNGI they also encode PHEROMONES and PHEROMONE RECEPTORS. The transcription factors control expression of specific proteins that give a cell its mating identity. Opposite mating type identities are required for mating.Gene Duplication: Processes occurring in various organisms by which new genes are copied. Gene duplication may result in a MULTIGENE FAMILY; supergenes or PSEUDOGENES.Uniparental Disomy: The presence in a cell of two paired chromosomes from the same parent, with no chromosome of that pair from the other parent. This chromosome composition stems from non-disjunction (NONDISJUNCTION, GENETIC) events during MEIOSIS. The disomy may be composed of both homologous chromosomes from one parent (heterodisomy) or a duplicate of one chromosome (isodisomy).DNA-Binding Proteins: Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases.Chromosomal Instability: An increased tendency to acquire CHROMOSOME ABERRATIONS when various processes involved in chromosome replication, repair, or segregation are dysfunctional.Spindle Apparatus: A microtubule structure that forms during CELL DIVISION. It consists of two SPINDLE POLES, and sets of MICROTUBULES that may include the astral microtubules, the polar microtubules, and the kinetochore microtubules.Snakes: Limbless REPTILES of the suborder Serpentes.Unsafe Sex: Sexual behaviors which are high-risk for contracting SEXUALLY TRANSMITTED DISEASES or for producing PREGNANCY.Rumex: A plant genus of the family POLYGONACEAE that contains patientosides and other naphthalene glycosides.Prenatal Diagnosis: Determination of the nature of a pathological condition or disease in the postimplantation EMBRYO; FETUS; or pregnant female before birth.Germ Cells: The reproductive cells in multicellular organisms at various stages during GAMETOGENESIS.Cell Nucleus: Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Chromosome Fragility: Susceptibility of chromosomes to breakage leading to translocation; CHROMOSOME INVERSION; SEQUENCE DELETION; or other CHROMOSOME BREAKAGE related aberrations.Gonads: The gamete-producing glands, OVARY or TESTIS.Polymorphism, Single Nucleotide: A single nucleotide variation in a genetic sequence that occurs at appreciable frequency in the population.Gene Deletion: A genetic rearrangement through loss of segments of DNA or RNA, bringing sequences which are normally separated into close proximity. This deletion may be detected using cytogenetic techniques and can also be inferred from the phenotype, indicating a deletion at one specific locus.Ploidies: The degree of replication of the chromosome set in the karyotype.Genome, Human: The complete genetic complement contained in the DNA of a set of CHROMOSOMES in a HUMAN. The length of the human genome is about 3 billion base pairs.DNA Transposable Elements: Discrete segments of DNA which can excise and reintegrate to another site in the genome. Most are inactive, i.e., have not been found to exist outside the integrated state. DNA transposable elements include bacterial IS (insertion sequence) elements, Tn elements, the maize controlling elements Ac and Ds, Drosophila P, gypsy, and pogo elements, the human Tigger elements and the Tc and mariner elements which are found throughout the animal kingdom.Struthioniformes: An order of flightless birds comprising the ostriches, which naturally inhabit open, low rainfall areas of Africa.Gene Rearrangement: The ordered rearrangement of gene regions by DNA recombination such as that which occurs normally during development.

*  Conserved sex chromosomes in iguanas | Biology Letters

... which suggests that iguanas may have conserved sex chromosomes [7]. At the same time, the sex chromosomes are very small ( ... possess a rapid turnover of sex chromosomes, while in endotherms there is a notable stability of sex chromosomes. Reptiles in ... other species have exhibited multiple and/or relatively large sex chromosomes, and in many other lineages sex chromosomes (if ... 2013 Novel sex-determining genes in fish and sex chromosome evolution. Dev. Dyn. 242, 339-353. (doi:10.1002/dvdy.23927). ...

*  The origin of sex chromosomes › News in Science (ABC Science)

"By fossil digging on the sex chromosomes, we were able to reconstruct the four events that drove sex chromosomes into their ... Each inversion drove the sex chromosomes farther apart as they evolved. Each piece of the chromosomes that inverted added to ... "The SRY-bearing chromosome became the Y chromosome and its SRY-deficient partner became the X chromosome," says Lahn. ... snapshot of sex chromosomes.. The X chromosome was found to have four groups of genes physically arranged as four consecutive ...

*  Evolution of sex chromosomes and sex-biased gene expression | Department of Biology

... a neo-sex chromosome, which has been formed by a fusion between an autosome and the ancestral sex chromosomes. This neo-sex ... Second, the neo-sex chromosome is homologous to the sex chromosomes of mammals, which makes it possible - for the first time - ... Sex chromosomes have evolved from non-sex-determining chromosomes (autosomes) many times throughout the tree of life. Ever ... Start › Research › Research groups › Genetics of Sex Differences › Research projects › Evolution of sex chromosomes and sex- ...

*  CSIRO PUBLISHING | Reproduction, Fertility and Development

RD09250Monotreme sex chromosomes - implications for the evolution of amniote sex chromosomes. Paul D. Waters and Jennifer A. ... RD09085Platypus chain reaction: directional and ordered meiotic pairing of the multiple sex chromosome chain in Ornithorhynchus ... RD09084Analysis of SINE and LINE repeat content of Y chromosomes in the platypus, Ornithorhynchus anatinus. R. Daniel Kortschak ... RD09099Replication asynchrony and differential condensation of X chromosomes in female platypus (Ornithorhynchus anatinus). ...

*  HHMI Scientists Search Results | Howard Hughes Medical Institute (HHMI)

Sex Chromosomes and Sex Differences Whitehead Institute for Biomedical Research Cambridge, MA ... Duplication of Eukaryotic Chromosomes Massachusetts Institute of Technology Cambridge, MA Tyler Jacks, PhD Investigator The Use ...

*  Free Science Flashcards about Child Psycology

The sex of a child is determined by the sex chromosomes of. the father. ... The chromosomes that do NOT determine sex are called. zygotes.. A cell that has divided through mitosis possesses __________, ... 23 pairs of chromosomes; 23 chromosomes. The idea that each child in a family grows up in a unique environment is referred to ... The normal complement of sex chromosomes for a woman is ___, and for a man it is ___.. XX; XY. ...

*  Brain Connectivity in Neurodevelopmental Disorders in Response to Treatment - Full Text View -

Sex Chromosome Disorders. Chromosome Disorders. Congenital Abnormalities. Genetic Diseases, Inborn. Genetic Diseases, X-Linked ...

*  National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Conditions - Full Text View -...

Disorders of Sex Development. Urogenital Abnormalities. Sex Chromosome Disorders of Sex Development. Heart Defects, Congenital ... Recurrent chromosome 16p13.1 duplications are a risk factor for aortic dissections. PLoS Genet. 2011 Jun;7(6):e1002118. doi: ... Autosomal and X chromosome structural variants are associated with congenital heart defects in Turner syndrome: The NHLBI ...

* (8169667) Scientists have patented a new machine that will provide orgasms for women at the push of a button, making...

The end of the Y chromosome was exaggerated:. Reports of Looming Male Extinction Exaggerated. Men's Y Sex Chromosome Is Here To ... Men's Y Sex Chromosome Is Here To Stay Despite Being 'Puny'; Evolution Will Prevent Male Fertility Genes From Demise, Study ... AcademGreen: There's also some debate as to whether or not the Y chromosome will decay within 5M years. Men could be made ... acohn: AcademGreen: There's also some debate as to whether or not the Y chromosome will decay within 5M years. Men could be ...

*  Publications

The mouse X chromosome is enriched for sex-biased genes not subject to selection by meiotic sex chromosome inactivation. Nat ... MDC1 directs chromosome-wide silencing of the sex chromosomes in male germ cells. Genes Dev. 2011 May 1; 25 (25; 9; 2011 May 1 ... Rsx is a metatherian RNA with Xist-like properties in X-chromosome inactivation. Nature. 2012 Jul 12; 487 (7406; 487; 2012 Jul ... X for intersection: retrotransposition both on and off the X chromosome is more frequent. Trends Genet. 2005 Jan; 21 (2005 Jan ...

*  A neoW chromosome drives speciation | Proceedings of the Royal Society of London B: Biological Sciences

2007 Sex chromosomes and sex determination in Lepidoptera. Sex. Dev. 1, 332-346. (doi:10.1159/000111765). ... W chromosome unfused; green, W chromosome fused. Wild-type bivalents (in a,b,d) comprise, respectively, two sex chromosomes (Z/ ... 2012 Sex chromosome evolution in moths and butterflies. Chromosome Res. 20, 83-94. (doi:10.1007/s10577-011-9262-z). ... sex chromosomes or both, and arguably unfit. However, karyotype J with an unfused W chromosome is probably the standard ...

*  A single female-specific piRNA is the primary determiner of sex in the silkworm. | Sigma-Aldrich

In this system, males have two Z sex chromosomes, whereas females have Z and W sex chromosomes. The silkworm W chromosome has a ... Fem sequences were arranged in tandem in the sex-determining region of the W chromosome. Inhibition of Fem-derived piRNA- ... Our study characterizes a single small RNA that is responsible for primary sex determination in the WZ sex determination system ... are the only known transcripts that are produced from the sex-determining region of the W chromosome, but the function(s) of ...

*  Why Too Many Sperms Spoil the Egg | Psychology Today

Excessive sperm numbers around an egg can result in multiple fertilization, abnormal chromosome numbers, and miscarriage. ... It was found to have 69 chromosomes, including three sex chromosomes (XXY). Features of certain chromosomes that could only ... but a sex cell contains only 23 (haploid number). A sex cell contains only a single sex chromosome, X in an egg and X or Y in a ... Extra chromosome sets directly harm sex determination. A triploid individual, for instance, has an abnormal combination of sex ...

*  Aberrant KLK4 gene promoter hypomethylation in pediatric hepatoblastomas

Chow J and Heard E: X inactivation and the complexities of silencing a sex chromosome. Curr Opin Cell Biol. 21:359-366. 2009. ... X-chromosome inactivation, genomic imprinting and chromatin modification (6-8). It is generally recognized that DNA methylation ...

*  Publications - Institut de Génomique Fonctionnelle de Lyon

Insights into Sex Chromosome Evolution and Aging from the Genome of a Short-Lived Fish. Author(s) : Reichwald K, Petzold A, ... Transposable elements and early evolution of sex chromosomes in fish. Author(s) : Chalopin D, Volff J, Galiana D, Anderson J, ... Journal : Chromosome Res. 2015. Altered retinoic acid signalling underpins dentition evolution. Author(s) : Gibert Y, Samarut E ... Sex hormones and their receptors in bone homeostasis: insights from genetically modified mouse models. Author(s) : Vico L, ...

*  X Chromosome Test

... ing is ideal to discover whether females have the same biological father. Contact our Dublin office for more ... Females have a total number of 46 chromosomes in every cell with 1 pair of XX chromosome (sex chromosomes). All females will ... The X chromosome test can be used between paternal grandmother and granddaughter as they must share one X chromosome. This ... X Chromosome Test. €399 Order now Are you sisters who have different mothers and want to know whether you have the same dad? If ...

*  Menstrual Cycle - STEP1 Reproductive - Step 1 -

Sex chromosome disorders * Turner Syndrome * Klinefelter Syndrome * XYY Syndrome * Pseudohermaphroditism * True Hermaphrodite ...

*  The Biologist Is In: My Seed Archive

Sex Chromosomes of the Triturus Newt. * ► Aug 2017 (2) * ► Jul 2017 (1) ...

*  Microdeletion syndromes (chromosomes 12 to 22)

... are usually microscopically visible on chromosome-banded karyotypes. Microdeletions, or submicroscopic deletions, are ... Chromosome deletions that span at least 5 megabases (Mb) ... Sex chromosome abnormalities. *Tools for genetics and genomics ... See 'Microdeletion syndromes (chromosomes 1 to 11)' and 'Microduplication syndromes' and 'Sex chromosome abnormalities' and ' ... Chromosome deletions that span at least 5 megabases (Mb) are usually microscopically visible on chromosome-banded karyotypes. ...

*  Serenity Non Invasive Testing - Newlife Fertility Clinic Surrey

Sex chromosome aneuploidies are conditions in which there is a change from the usual 2 copies of sex chromosomes in males (XY) ... Tests for sex chromosome conditions (for singleton pregnancies) or the presence of a Y chromosome (for twin pregnancies) ... We all carry 23 pairs of chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes), which are made of DNA, in every ... The Serenity prenatal test® only tests for aneuploidies of chromosomes 13, 18, 21, and sex chromosomes (for singleton ...

*  First Trimester Screening - Health Encyclopedia - University of Rochester Medical Center

It checks for certain abnormal chromosomes. It can also check for defects in the fetal sex chromosomes (X or Y). Cell-free ... Abnormal levels could mean an increased risk for a chromosome defect. *Human chorionic gonadotropin (hCG). This hormone is made ... This includes chromosome defects such as Down syndrome (trisomy 21), or trisomy 18 or 13. ...

*  Amenorrhea |

In other girls, the delay of menses may be due to Turner's syndrome, a genetic disorder involving the sex chromosomes, or to a ... an altered sex drive, breast milk secretions, weight gain, or several or all these symptoms. ... a young girl may be given supplemental ovarian hormones to allow her to develop normal secondary sex characteristics (breast ...

*  Publications - Howard Hughes Medical Institute Programs

Sex chromosome meiotic drive in stalk-eyed flies. Genetics 147: 1169-1180. ... Intraspecific variation in fem-3 and tra-2, two rapidly coevolving nematode sex-determining genes. Gene 349: 35-42. ... Comparative genetics of sex-determination: Masculinizing mutations in Caenorhabditis briggsae. Genetics 178: 1415-1429. ... Intraspecific variation in fem-3 and tra-2, two rapidly coevolving nematode sex-determining genes. GENE 349: 35-42. ...

*  Clinical manifestations and diagnosis of Turner syndrome

It is caused by loss of part or all of an X chromosome.The clinical manifestations and d ... Turner syndrome is one of the most common chromosome anomalies in humans and represents an important cause of short stature and ... Turner syndrome is one of the most common sex chromosome abnormalities in females and occurs in approximately 1 in 2000 to 1 in ... Mosaicism in 45,X Turner syndrome: does survival in early pregnancy depend on the presence of two sex chromosomes? Hum Genet ...

*  NESCent: The National Evolutionary Synthesis Center

Several striking phenomena within the family indicate it can become a model system for investigating sex-chromosome evolution, ...

Premature chromosome condensation: Premature chromosome condensation (PCC) occurs in eukaryotic organisms when mitotic cells fuse with interphase cells. Chromatin, a substance that contains genetic material such as DNA, is normally found in a loose bundle inside a cell's nucleus.Chromosome regionsSmith–Fineman–Myers syndrome: Smith–Fineman–Myers syndrome (SFMS1), also called X-linked mental retardation-hypotonic facies syndrome 1 (MRXHF1), Carpenter–Waziri syndrome, Chudley–Lowry syndrome, SFMS, Holmes–Gang syndrome and Juberg–Marsidi syndrome (JMS), is a rare X-linked recessive congenital disorder that causes birth defects. This syndrome was named after 3 men, Richard D.PCDHY: PCDH11Y is a gene unique to human males which competes with FOXP2 for the title of the "language gene." PCDH11Y is the gene for making Protocadherin 11Y, a protein that guides the development of nerve cells.Genetic imbalance: Genetic imbalance is to describe situation when the genome of a cell or organism has more copies of some genes than other genes due to chromosomal rearrangements or aneuploidy.Suresh Jayakar: Suresh Dinakar Jayakar (21 September 1937, Bombay-21 January 1988) was an Indian biologist who pioneered in the use of quantitative approaches in genetics and biology.Silene undulataImmortal DNA strand hypothesis: The immortal DNA strand hypothesis was proposed in 1975 by John Cairns as a mechanism for adult stem cells to minimize mutations in their genomes.Cairns, J.Circular bacterial chromosome: A circular bacterial chromosome is a bacterial chromosome in the form of a molecule of circular DNA. Unlike the linear DNA of most eukaryotes, typical bacterial chromosomes are circular.Platypus venomPolysomy: Polysomy is a condition found in many species, including fungi, plants, insects, and mammals, in which an organism has at least one more chromosome than normal, i.e.Transient neonatal diabetes mellitusSpermatocyte: Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia.Genetic linkage: Genetic linkage is the tendency of alleles that are located close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Genes whose loci are nearer to each other are less likely to be separated onto different chromatids during chromosomal crossover, and are therefore said to be genetically linked.Molecular evolution: Molecular evolution is a change in the sequence composition of cellular molecules such as DNA, RNA, and proteins across generations. The field of molecular evolution uses principles of evolutionary biology and population genetics to explain patterns in these changes.Skewed X-inactivation: Skewed X chromosome inactivation occurs when the inactivation of one X chromosome is favored over the other, leading to an uneven number of cells with each chromosome inactivated. It is usually defined as one allele being found on the active X chromosome in over 75% of cells, and extreme skewing is when over 90% of cells have inactivated the same X chromosome.Papaya ringspot virus: Papaya ringspot virus (PRSV) is a pathogenic plant virus in the genus Potyvirus and the virus family Potyviridae.Confined placental mosaicism: Confined placental mosaicism (CPM) represents a discrepancy between the chromosomal makeup of the cells in the placenta and the cells in the baby. CPM was first described by Kalousek and Dill in 1983.Recombination (cosmology): In cosmology, recombination refers to the epoch at which charged electrons and protons first became bound to form electrically neutral hydrogen atoms.Note that the term recombination is a misnomer, considering that it represents the first time that electrically neutral hydrogen formed.John Payne ToddColes PhillipsCentromereWilliam Lakin Turner: William Lakin Turner (25 February 1867 – 21 October 1936) was an English landscape artist.Symmetry element: A symmetry element is a point of reference about which symmetry operations can take place. In particular, symmetry elements can be centers of inversion, axes of rotation and mirror planes.Oncogene: An oncogene is a gene that has the potential to cause cancer.Wilbur, Beth, editor.Ring chromosome: A ring chromosome is a chromosome whose arms have fused together to form a ring. Ring chromosomes were first discovered by Lilian Vaughan Morgan in 1926.List of diseases (M): This is a list of diseases starting with the letter "M".Trisomy 9Metaphase: Metaphase (from the Greek μετά, "adjacent" and φάσις, "stage") is a stage of mitosis in the eukaryotic cell cycle in which chromosomes are at their second-most condensed and coiled stage (they are at their most condensed in anaphase. These chromosomes, carrying genetic information, align in the equator of the cell before being separated into each of the two daughter cells.Spermiogenesis: Spermiogenesis is the final stage of spermatogenesis, which sees the maturation of spermatids into mature, motile spermatozoa. The spermatid is more or less circular cell containing a nucleus, Golgi apparatus, centriole and mitochondria.Microsatellite: A microsatellite is a tract of repetitive DNA in which certain DNA motifs (ranging in length from 2–5 base pairs) are repeated, typically 5-50 times. Microsatellites occur at thousands of locations in the human genome and they are notable for their high mutation rate and high diversity in the population.

(1/1051) Assaying potential carcinogens with Drosophila.

Drosophila offers many advantages for the detection of mutagenic activity of carcinogenic agents. It provides the quickest assay system for detecting mutations in animals today. Its generation time is short, and Drosophila is cheap and easy to breed in large numbers. The simple genetic testing methods give unequivocal answers about the whole spectrum of relevant genetic damage. A comparison of the detection capacity of assays sampling different kinds of genetic damage revealed that various substances are highly effective in inducing mutations but do not produce chromosome breakage effects at all, or only at much higher concentrations than those required for mutation induction. Of the different assay systems available, the classical sex-linked recessive lethal test deserves priority, in view of its superior capacity to detect mutagens. Of practical importance is also its high sensitivity, because a large number of loci in one fifth of the genome is tested for newly induced forward mutations, including small deletions. The recent findings that Drosophila is capable of carrying out the same metabolic activation reactions as the mammalian liver makes the organism eminently suitable for verifying results obtained in prescreening with fast microbial assay systems. An additional advantage in this respect is the capacity of Drosophila for detecting short-lived activation products, because intracellular metabolic activation appears to occur within the spermatids and spermatocytes.  (+info)

(2/1051) Enzymes and reproduction in natural populations of Drosophila euronotus.

Populations of Drosophila euronotus, one from southern Louisiana )3 samples), and one from Missouri (2 samples), were classified for allele frequencies at alkaline phosphatase (APH) and acid phosphatase (ACPH) loci. The two populations differed consistently in allele frequencies at both loci. The APH locus is on the inversion-free X chromosome; the chromosomal locus of the autosomal ACPH is unknown, and could involve inversion polymorphism. Wild females from Missouri and Louisiana populations heterozygous at the APH locus carried more sperm at capture than did the corresponding homozygotes. This heterotic association was significant for the combined samples, and whether it was the result of heterosis at the enzyme locus studied, or due to geographically widespread close linkage with other heterotic loci, it should help to maintain heterozygosity at the APH locus. In a Louisiana collection which included large numbers of sperm-free females, simultaneous homozygosity at both enzyme loci was significantly associated with lack of sperm. It is suggested that the latter association is the result of young heterozygous females achieving sexual maturity earlier than do the double homozygotes. The average effective sperm load for 225 wild females was only 29.4, suggesting the necessity for frequent repeat-mating in nature to maintain female fertility. A comparison of the sex-linked APH genotypes of wild females with those of their daughters indicated that among 295 wild-inseminated females from five populations, 35% had mated more than once, and of this 35%, six females had mated at least three times. Because of ascertainment difficulties, it is clear that the true frequency of multiple-mating in nature must have been much higher than the observed 35%. Laboratory studies indicate that multiple-mating in this species does not involve sperm displacement, possibly due to the small number of sperms transmitted per mating, and the fact that the sperm receptacles are only partially filled by a given mating.  (+info)

(3/1051) An unusual family of benign "X" linked muscular dystrophy with cardiac involvement.

A family of benign X-linked muscular dystrophy is described. Two of the 3 affected members appear quite representative of Becker's dystrophy. A third shows no pseudohypertrophy, only gross atrophy, affecting proximal and distal muscles and also shows early onset contractures and electrocardiographic abnormalities and is in these ways much more representative of the variety described by Emery and Dreifuss (1966). Two of the cases have distinctly abnormal electrocardiograms with extensive and deep Q waves and abnormal R/S ratios and VI. Both these have shown progression of electrocardiographic abnormalities during a 2-year follow-up. The family is reported to document this very unusual occurrence.  (+info)

(4/1051) Linkage relations of locus for X-borne type of Charcot-Marie-Tooth muscular atrophy and that for Xg blood groups.

The locus for the X-borne type of Charcot-Marie-Tooth muscular atrophy is not close to the Xg locus and probably not within direct measurable distance of it.  (+info)

(5/1051) Mitotic recombination in the heterochromatin of the sex chromosomes of Drosophila melanogaster.

The frequency of spontaneous and X-ray-induced mitotic recombination involving the Y chromosome has been studied in individuals with a marked Y chromosome arm and different XY compound chromosomes. The genotypes used include X chromosomes with different amounts of X heterochromatin and either or both arms of the Y chromosome attached to either side of the centromere. Individuals with two Y chromosomes have also been studied. The results show that the bulk of mitotic recombination takes place between homologous regions.  (+info)

(6/1051) Dicentric X isochromosomes in man.

Four cases of Turner's syndrome are presented in which an apparent X isochromosome i(Xq) has been found to possess two regions of centromeric heterochromatin. It is suggested that these chromosomes were isodicentric structures capable of functioning as monocentric elements as a result of the inactivation of one centromere. The prevalence of mosaicism is believed to be a consequence of the dicentric nature of these chromosomes, and it is considered possible that a high proportion of X isochromosmes are structurally dicentric. Banding patterns showed that the exchange site involved in the formation of the dicentric chromosome was different in at least three of the cases.  (+info)

(7/1051) Triple X female and Turner's syndrome offspring.

A mentally retarded young female having 47 chromosomes with a triple X karotype produced a child with Turner's syndrome associated with mental defeciency. To our knowledge this is the first example of a triple X female giving birth to a child with Turner's syndrome.  (+info)

(8/1051) Volumetric magnetic resonance imaging study of the brain in subjects with sex chromosome aneuploidies.

OBJECTIVES: Cognitive impairment has been reported in people with sex chromosome aneuploides (SCAs) and it has been proposed that the presence of an extra sex chromosome may have an adverse effect on neurodevelopment. This study examines the hypothesis with structural MRI of the brain. METHODS: Thirty two subjects with SCA (XXX (n=12), XYY (n=10), and XXY (n=10)) from a birth cohort study were matched groupwise for age, parental social class, and height with normal controls (13 female, 26 male). Brain MRI, measurements of IQ, and a structured psychiatric interview were performed. RESULTS: The XXX females and XXY males had significantly smaller whole brain volumes than controls of the same phenotypic sex (p=0.003 and p+info)

interplay between sex

  • To understand the interplay between sex chromosomes and sexual conflicts by studying whether sexually antagonistic mutations accumulate on sex chromosomes, and whether sexual conflicts drive sex chromosome evolution. (
  • Our results demonstrate how a complex interplay between sex, colour pattern, male-killing, and a neo-W chromosome, has set up a genetic 'sink' that keeps the two subspecies apart. (


  • This was when one of the autosomes mutated and acquired the SRY gene -- Sex-determining Region Y -- which is the master switch for creating a male. (
  • Sex chromosomes have evolved from non-sex-determining chromosomes (autosomes) many times throughout the tree of life. (
  • We all carry 23 pairs of chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes), which are made of DNA, in every cell of our body. (


  • We demonstrate that members of the New World families Iguanidae, Tropiduridae, Leiocephalidae, Phrynosomatidae, Dactyloidae and Crotaphytidae, as well as of the family Opluridae which is restricted to Madagascar, all share homologous sex chromosomes. (
  • Second, the neo-sex chromosome is homologous to the sex chromosomes of mammals, which makes it possible - for the first time - to study mammalian X gene homologs in a novel, avian Z-linked environment where females are the heterogametic sex (ZW), and thus to draw direct parallels over the avian ZW-mammalian XY boundary. (

sexually antagonistic

  • Finally, we use our unique 30-year ecological dataset and rich collection of DNA samples of the great reed warbler to test the widely accepted but poorly supported sexual antagonism hypothesis suggesting that sexually antagonistic mutations accumulate on the sex chromosomes and drive their evolution. (
  • Sexually antagonistic selection can drive both the evolution of sex chromosomes and speciation itself. (
  • The tropical butterfly the African Queen, Danaus chrysippus , shows two such sexually antagonistic phenotypes, the first being sex-linked colour pattern, the second, susceptibility to a male-killing, maternally inherited mollicute, Spiroplasma ixodeti , which causes approximately 100% mortality in male eggs and first instar larvae. (


  • Most likely this suppression was the result of a series of chromosomal inversions on the Y chromosome, which would also explain why the genes appear to be in order on the X but scrambled on the Y," Page explains. (
  • You have a personal or family history of chromosomal aneuploidies for trisomy 13, 18, 21, or other sex chromosome aneuploidies. (

extra chromosome

  • An egg fertilized by three sperms receives two extra chromosome sets, resulting in a quadruploid individual with 92 chromosomes. (
  • Extra chromosome sets directly harm sex determination. (
  • Trisomy 21 (Down syndrome) is due to an extra chromosome 21 and is the most common trisomy at the time of birth. (
  • Trisomy 18 (Edwards syndrome) is due to an extra chromosome 18 and is associated with a high rate of miscarriage. (
  • Trisomy 13 (Patau syndrome) is due to an extra chromosome 13 and is associated with a high rate of miscarriage. (


  • Although the genetic framework for the differentiation of testes or ovaries is highly conserved [ 1 ], the process called sex determination, responsible for the decision whether the undifferentiated gonad will turn into a testis or ovary, is surprisingly variable. (
  • Some lineages of reptiles, e.g. dragon lizards or geckos [ 7 - 9 ], exhibit a large variability in sex determination, but based on the phylogenetic distribution of male and female heterogamety, other lineages may possess conserved sex chromosomes [ 7 , 10 ]. (
  • Ever since their discovery, these chromosomes have captivated researchers because of their obvious involvement in fundamental aspects of an organism's life, such as sex determination, sexual reproduction and sexual conflicts. (
  • The silkworm Bombyx mori uses a WZ sex determination system that is analogous to the one found in birds and some reptiles. (
  • The silkworm W chromosome has a dominant role in female determination, suggesting the existence of a dominant feminizing gene in this chromosome. (
  • Our study characterizes a single small RNA that is responsible for primary sex determination in the WZ sex determination system. (


  • Microdeletion syndromes involving chromosomes 1 through 11 are discussed separately, as are microduplication syndromes and congenital abnormalities of the sex chromosomes. (
  • See 'Microdeletion syndromes (chromosomes 1 to 11)' and 'Microduplication syndromes' and 'Sex chromosome abnormalities' and 'Congenital cytogenetic abnormalities' . (
  • The most common chromosome abnormalities include Down's syndrome (trisomy 21), Edward's syndrome (trisomy 18) and Patau syndrome (trisomy 13). (


  • In this system, males have two Z sex chromosomes, whereas females have Z and W sex chromosomes. (
  • Females have a total number of 46 chromosomes in every cell with 1 pair of XX chromosome (sex chromosomes). (
  • All females will share an identical X chromosome with their biological father. (
  • Identical X chromosome profiles means the females tested share the same birth father. (
  • X chromosome testing is ideally done between females who have different biological mothers and who need to confirm whether or not they have the same biological father. (
  • Sex chromosome aneuploidies are conditions in which there is a change from the usual 2 copies of sex chromosomes in males (XY) or females (XX). (
  • Females usually have two X chromosomes and males have one X and one Y chromosome. (


  • Our research focuses mainly on Sylvioidea passerine birds where we have recently detected a new sex chromosome, a neo-sex chromosome, which has been formed by a fusion between an autosome and the ancestral sex chromosomes. (
  • Here we show that a neo-W chromosome, a fusion between the W (female) chromosome and an autosome that controls both colour pattern and male-killing, links the two phenotypes thereby driving speciation across the hybrid zone. (


  • First the researchers compared the locations of the 19 fossil gene pairs on the human X and Y chromosomes. (
  • We are now exploring this remarkable neo-sex chromosome system to understand the evolution of sex chromosomes in terms of recombination cessation and gene content. (
  • To understand sex chromosome evolution in terms of recombination cessation, degeneration and gene content. (
  • To understand the evolution of sex-biased gene expression and dosage compensation, and whether incomplete dosage compensation disrupts critical gene co-expression networks. (
  • However, the W chromosome is almost fully occupied by transposable element sequences, and no functional protein-coding gene has been identified so far. (
  • Inhibition of Fem-derived piRNA-mediated signalling in female embryos led to the production of the male-specific splice variants of B. mori doublesex (Bmdsx), a gene which acts at the downstream end of the sex differentiation cascade. (
  • A target gene of Fem-derived piRNA was identified on the Z chromosome of B. mori. (
  • DNA methylation is the only genetically programmed DNA modification process in mammals that is involved in the regulation of various biological processes, including gene transcription, X-chromosome inactivation, genomic imprinting and chromatin modification ( 6 - 8 ). (


  • Molecular or molecular-cytogenetic data which would enable the testing of the evolutionary stability of sex chromosomes are, however, lacking for most reptilian lineages. (
  • Researchers at the Howard Hughes Medical Institute have found that the X and Y chromosomes evolved from a standard identical pair around 300 million years ago - shortly after the divergence of the evolutionary lines leading to mammals and birds. (
  • 19 genes shared between the X and Y served as the "fossils" that helped Lahn and Page to reconstruct the evolutionary history of sex chromosomes. (


  • Nevertheless, many genes on the human Y chromosome have homologues (analogous genes) on the X chromosome. (
  • The reconstruction of the defining events of human sex-chromosome evolution is analogous to the reconstruction of the evolution of species, except that we are looking at changes of a pair of chromosomes over geologic time rather than changes of whole organisms," says Lahn. (


  • Page and Lahn say differentiation between the two chromosomes could have occurred only after recombination between the X-Y genes was suppressed. (


  • Recombination, which is the process of swapping bits of genetic material between a pair of chromosomes during the formation of eggs or sperm, is essential to maintaining genetic identity between X and Y. Without it, the two chromosomes would diverge into completely distinct forms. (


  • Iguanas thus show a stability of sex chromosomes comparable to mammals and birds and represent the group with the oldest sex chromosomes currently known among amniotic poikilothermic vertebrates. (
  • Some poikilothermic lineages, such as several well-studied groups of fish or frogs, possess a rapid turnover of sex chromosomes [ 2 , 3 ], while endotherms, i.e. mammals and birds, have highly conserved sex chromosomes. (
  • To evaluate possible convergent evolution of the same sex-linked genes in birds and mammals. (


  • This lack of detailed knowledge about sex chromosome evolution compromises our understanding of fundamental biological questions (e.g. the evolution of sexual conflicts) as well as more practical ones (e.g. about sex-linked genetic diseases). (
  • With this test we only look at genetic markers specific to the X chromosome, seeking for a match in profiles between the individuals tested. (
  • The Serenity prenatal test® measures genetic material (DNA) from a pregnant woman's blood to look for too few or too many copies of chromosomes (referred to as aneuploidies) in the mother and baby. (


  • Here, we focus on the testing of the homology of sex chromosomes across iguanas (Pleurodonta)-the ancient, species-rich (more than 1080 recent species [ 13 ]) and highly diversified group of lizards. (


  • Here, we provide molecular evidence that sex chromosomes are highly conserved across iguanas, one of the most species-rich clade of reptiles. (
  • As poikilotherms, reptiles (the term 'reptiles' denotes here the paraphyletic group, i.e. sauropsids with the exclusion of their inner avian group) are usually considered as a group with a rapid turnover of sex-determining mechanisms [ 4 , 5 ] and as a whole, they indeed exhibit a large variability in sex-determining systems [ 6 , 7 ]. (


  • When sex cells (eggs and sperms) are produced, the usual number of chromosomes is halved. (


  • Of our 46 human chromosomes, 44 form matched pairs. (


  • At the same time, the sex chromosomes are very small (microchromosomes) and morphologically poorly differentiated in many species, so that it is impossible to evaluate the homology of sex chromosomes based only on their appearance. (


  • Current screening options can tell you the chance (for example, 1 in 50 or 1 in 5000) of your pregnancy having a certain chromosome problem, but they do not provide a definitive answer. (


  • However, the rate of turnover of sex-determining mechanisms is notably different among particular vertebrate lineages. (
  • Only afterwards do special mechanisms make sure that just one set of male chromosomes contributes to the offspring. (


  • Page and colleague Dr Bruce Lahn reconstructed the stages of sex chromosome evolution, and the time course over which these chromosomes were built. (
  • By fossil digging on the sex chromosomes, we were able to reconstruct the four events that drove sex chromosomes into their distinctive X and Y forms, and to date when these events occurred during evolution," says Lahn. (


  • Diagram of a human sperm showing the nucleus containing a haploid set of 23 chromosomes in its head. (
  • A sex cell contains only a single sex chromosome, X in an egg and X or Y in a sperm. (
  • Fusion of a sperm with an egg at fertilization restores the normal chromosome number, and approximately equal numbers of female (XX) and male (XY) offspring are produced. (


  • They then compared the number of mutations between the X form and the Y form of a pair of X-Y genes to come up with rough estimates of when they were last alike, giving them a 'geologic' snapshot of sex chromosomes. (
  • If two sperms fertilize an egg, things go wildly wrong, yielding a triploid offspring with 69 chromosomes with an extra set in addition to the normal maternal/paternal pair. (


  • Monosomy X, also called Turner syndrome, is a condition caused by the absence of the second X chromosome in a female. (


  • This is an ideal situation for research on sex chromosomes, because the processes we wish to study have had some time to leave detectable genomic footprints, but have not yet removed the material we want to investigate. (
  • X chromosome testing results have a turnaround time of 17-15 working days . (


  • Human body cells typically have 46 chromosomes ( diploid number ), but a sex cell contains only 23 ( haploid number ). (


  • A single female-specific piRNA is the primary determiner of sex in the silkworm. (
  • The set includes a single sex chromosome, either an X or a Y. (


  • As our sampling represents the majority of the phylogenetic diversity of iguanas, the origin of iguana sex chromosomes can be traced back in history to the basal splitting of this group which occurred during the Cretaceous period. (


  • Here we show that a W-chromosome-derived, female-specific piRNA is the feminizing factor of B. mori. (


  • This neo-sex chromosome is evolutionarily very interesting and promising for research: First, the female-specific neo-W chromosome is in an intermediate stage of degeneration. (


  • Colubroid snakes represent a notable exception with a demonstration of sex chromosome conservation for at least 40 Ma [ 11 , 12 ]. (
  • The first events that created the sex chromosomes had been thought to have occurred at least 170 million years ago," says researcher Dr David Page. (
  • Chromosome deletions that span at least 5 megabases (Mb) are usually microscopically visible on chromosome-banded karyotypes. (


  • It is therefore possible that different chromosomes were independently co-opted for the function of sex chromosomes in various lineages of iguanas. (
  • Female-enriched PIWI-interacting RNAs (piRNAs) are the only known transcripts that are produced from the sex-determining region of the W chromosome, but the function(s) of these piRNAs are unknown. (


  • However, molecular data which would enable the testing of the stability of sex chromosomes are lacking in most lineages. (


  • Moreover, other species have exhibited multiple and/or relatively large sex chromosomes, and in many other lineages sex chromosomes (if any) have remained undetected [ 14 ]. (


  • The X chromosome test can be used between paternal grandmother and granddaughter as they must share one X chromosome. (


  • Trisomies occur when three instead of the usual two copies of a chromosome are present. (


  • Fem sequences were arranged in tandem in the sex-determining region of the W chromosome. (
  • Compound heterozygous microdeletion of chromosome 15q13.3 region in a child with hypotonia, impaired vision, and global developmental delay. (


  • Karyotype data have shown that, wherever sex chromosomes are known, male heterogamety is present among iguanas, which suggests that iguanas may have conserved sex chromosomes [ 7 ]. (


  • The X chromosome was found to have four groups of genes physically arranged as four consecutive blocks, like the layers of rock in geological strata. (


  • Theoretical studies of male-killing endosymbionts, where hybridizing subpopulations interbreed, have shown that local adaptation can be strongly impeded in the subpopulation with the more biased population sex ratio [ 3 ]. (


  • If this is the case, then X chromosome testing is the ideal testing test. (
  • I had an X chromosome test with a potential half sister, the test results came back over a week before they were due. (
  • The tissue is then sent to a laboratory to test the chromosomes. (


  • In contrast, the groups appeared to be scrambled on the Y chromosome. (


  • If female siblings have the same mother we cannot offer X chromosome testing, unless the sample of the mother is available for analysis . (