Heterozygote
Tay-Sachs Disease
Hexosaminidase A
Encyclopedias as Topic
beta-N-Acetylhexosaminidases
Nervous System Diseases
Lipidoses
Journal Impact Factor
Access to Information
Publishing
Estimating the effective number of breeders from heterozygote excess in progeny. (1/1398)
The heterozygote-excess method is a recently published method for estimating the effective population size (Ne). It is based on the following principle: When the effective number of breeders (Neb) in a population is small, the allele frequencies will (by chance) be different in males and females, which causes an excess of heterozygotes in the progeny with respect to Hardy-Weinberg equilibrium expectations. We evaluate the accuracy and precision of the heterozygote-excess method using empirical and simulated data sets from polygamous, polygynous, and monogamous mating systems and by using realistic sample sizes of individuals (15-120) and loci (5-30) with varying levels of polymorphism. The method gave nearly unbiased estimates of Neb under all three mating systems. However, the confidence intervals on the point estimates of Neb were sufficiently small (and hence the heterozygote-excess method useful) only in polygamous and polygynous populations that were produced by <10 effective breeders, unless samples included > approximately 60 individuals and 20 multiallelic loci. (+info)Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency. (2/1398)
Primary carnitine deficiency is an autosomal recessive disorder of fatty acid oxidation caused by defective carnitine transport. This disease presents early in life with hypoketotic hypoglycemia or later in life with skeletal myopathy or cardiomyopathy. The gene for this condition maps to 5q31.2-32 and OCTN2, an organic cation/carnitine transporter, also maps to the same chromosomal region. Here we test the causative role of OCTN2 in primary carnitine deficiency by searching for mutations in this gene in affected patients. Fibroblasts from patients with primary carnitine deficiency lacked mediated carnitine transport. Transfection of patient's fibroblasts with the OCTN2 cDNA partially restored carnitine transport. Sequencing of the OCTN2 gene revealed different mutations in two unrelated patients. The first patient was homozygous (and both parents heterozygous) for a single base pair substitution converting the codon for Arg-282 to a STOP codon (R282X). The second patient was a compound heterozygote for a paternal 1-bp insertion producing a STOP codon (Y401X) and a maternal 1-bp deletion that produced a frameshift creating a subsequent STOP codon (458X). These mutations decreased the levels of mature OCTN2 mRNA and resulted in nonfunctional transporters, confirming that defects in the organic cation/carnitine transporter OCTN2 are responsible for primary carnitine deficiency. (+info)Novel mutation of the P0 extracellular domain causes a Dejerine-Sottas syndrome. (3/1398)
A patient is described with a Dejerine-Sottas syndrome caused by a novel heterozygous Cys(98)Tyr mutation in the extracellular domain of the major peripheral myelin protein zero (P0ex). Homotypical interactions between P0ex tetramers of apposed extracellular faces of the Schwann cell membrane play a crucial part in myelin compaction. The amino acid change disrupts a unique disulphide bond that stabilises the immunoglobulin-like structure of P0ex and it is predicted to cause severe dehypomyelination through dominant negative effects on the wild type protein. (+info)Requirement for the c-Maf transcription factor in crystallin gene regulation and lens development. (4/1398)
The vertebrate lens is a tissue composed of terminally differentiated fiber cells and anterior lens epithelial cells. The abundant, preferential expression of the soluble proteins called crystallins creates a transparent, refractive index gradient in the lens. Several transcription factors such as Pax6, Sox1, and L-Maf have been shown to regulate lens development. Here we show that mice lacking the transcription factor c-Maf are microphthalmic secondary to defective lens formation, specifically from the failure of posterior lens fiber elongation. The marked impairment of crystallin gene expression observed is likely explained by the ability of c-Maf to transactivate the crystallin gene promoter. Thus, c-Maf is required for the differentiation of the vertebrate lens. (+info)Iron overload in porphyria cutanea tarda. (5/1398)
BACKGROUND AND OBJECTIVE: Porphyria cutanea tarda (PCT) is a disorder of porphyrin metabolism associated with decreased activity of uroporphyrinogen decarboxylase (URO-D) in the liver. The relevance of iron in the pathogenesis of PCT is well established: iron overload is one of the factors that trigger the clinical manifestations of the disease and iron depletion remains the cornerstone of therapy for PCT. A role for genetic hemochromatosis in the pathogenesis of iron overload in PCT has been hypothesized in the past but only after the recent identification of the genetic defect causing hemochromatosis has the nature of this association been partially elucidated. This review will outline current concepts of the pathophysiology of iron overload in PCT as well as recent contributions to the molecular epidemiology of hemochromatosis defects in PCT. EVIDENCE AND INFORMATION SOURCES: The authors of the present review have a long-standing interest in the pathogenesis, etiology and epidemiology of iron overload syndromes. Evidence from journal articles covered by the Science Citation Index(R) and Medline(R) has been reviewed and collated with personal data and experience. STATE OF THE ART AND PERPECTIVES: Mild to moderate iron overload plays a key role in the pathogenesis of PCT. The recent identification of genetic mutations of the hemochromatosis gene (HFE) in the majority of patients with PCT confirms previous hypotheses on the association between PCT and hemochromatosis, allows a step forward in the understanding of the pathophysiology of the disturbance of iron metabolism in the liver of PCT patients, and provides an easily detectable genetic marker which could have a useful clinical application. Besides the epidemiological relevance of the association between PCT and hemochromatosis, however, it remains to be fully understood how iron overload, and in particular the cellular modifications of the iron status secondary to hemochromatosis mutations, affect the activity of URO-D, and how the altered iron metabolism interacts with the other two common triggers for PCT and etiological agents for the associated liver disease: alcohol and hepatitis viruses. The availability of a genetic marker for hemochromatosis will allow some of these issues to be addressed by studying aspects of porphyrins and iron metabolism in liver samples obtained from patients with PCT, liver disease of different etiology and different HFE genotypes, and by in vitro studies on genotyped cells and tissues. (+info)The obese gene is expressed in lean littermates of the genetically obese mouse (C57BL/6J ob/ob). (6/1398)
Some individuals of the mixed group of "lean" littermates (+/ob and +/+) of (C57BL/6J ob/ob) often suggest phenotypic characteristics of ob/ob animals. Therefore, it was of interest to determine whether expression of the ob gene had physiological significance in +/ob animals. Body weight (BW), fasting blood glucose (FBG), and body core temperature (Tr) were monitored between 62 and 364 days of age in +/+ and +/ob mice. Among females but not males, +/ob mice were heavier (P = 0.003) and FBG levels were greater (P = 0.04) than in +/+ animals. Comparison of Tr indicated differences suggesting falling Tr in +/ob but rising Tr in +/+ mice with age in males but not females. Multivariate analysis of variance yielded genotype effects for both males (P = 0.002) and females (P = 0.02). BW, FBG, and Tr alone were sufficient at the 75% level for genotypic characterization and separation of +/? animals as +/ob or +/+; clearly, expression of the ob gene in heterozygotes of the +/ob animal may make the mixed +/? group inappropriate as lean controls. (+info)Quantitative analysis of survival motor neuron copies: identification of subtle SMN1 mutations in patients with spinal muscular atrophy, genotype-phenotype correlation, and implications for genetic counseling. (7/1398)
Problems with diagnosis and genetic counseling occur for patients with autosomal recessive proximal spinal muscular atrophy (SMA) who do not show the most common mutation: homozygous absence of at least exon 7 of the telomeric survival motor neuron gene (SMN1). Here we present molecular genetic data for 42 independent nondeleted SMA patients. A nonradioactive quantitative PCR test showed one SMN1 copy in 19 patients (45%). By sequencing cloned reverse-transcription (RT) PCR products or genomic fragments of SMN1, we identified nine different mutations in 18 of the 19 patients, six described for the first time: three missense mutations (Y272C, T274I, S262I), three frameshift mutations in exons 2a, 2b, and 4 (124insT, 241-242ins4, 591delA), one nonsense mutation in exon 1 (Q15X), one Alu-mediated deletion from intron 4 to intron 6, and one donor splice site mutation in intron 7 (c.922+6T-->G). The most frequent mutation, Y272C, was found in 6 (33%) of 18 patients. Each intragenic mutation found in at least two patients occurred on the same haplotype background, indicating founder mutations. Genotype-phenotype correlation allowed inference of the effect of each mutation on the function of the SMN1 protein and the role of the SMN2 copy number in modulating the SMA phenotype. In 14 of 23 SMA patients with two SMN1 copies, at least one intact SMN1 copy was sequenced, which excludes a 5q-SMA and suggests the existence of further gene(s) responsible for approximately 4%-5% of phenotypes indistinguishable from SMA. We determined the validity of the test, and we discuss its practical implications and limitations. (+info)Radiation-induced G1 arrest is not defective in fibroblasts from Li-Fraumeni families without TP53 mutations. (8/1398)
Radiation-induced G1 arrest was studied in four classes of early passage skin fibroblasts comprising 12 normals, 12 heterozygous (mut/wt) TP53 mutation-carriers, two homozygous (mut/-) TP53 mutation-carriers and 16 strains from nine Li-Fraumeni syndrome or Li-Fraumeni-like families in which no TP53 mutation has been found, despite sequencing of all exons, exon-intron boundaries, 3' and 5' untranslated regions and promoter regions. In an assay of p53 allelic expression in yeast, cDNAs from these non-mutation strains behaved as wild-type p53. Using two different assays, we found G1 arrest was reduced in heterozygous strains with mis-sense mutations and one truncation mutation, when compared to the range established for the normal cells. Heterozygous strains with mutations at splice sites behaved like normal cells, whilst homozygous (mut/-) strains showed either extremely reduced, or no, arrest. Strains from all nine non-mutation families gave responses within the normal range. Exceptions to the previously reported inverse correlation between G1 arrest and clonogenic radiation resistance were observed, indicating that these phenotypes are not strictly interdependent. (+info)Heterozygote detection is a method used in genetics to identify individuals who carry one normal and one mutated copy of a gene. These individuals are known as heterozygotes and they do not typically show symptoms of the genetic disorder associated with the mutation, but they can pass the mutated gene on to their offspring, who may then be affected.
Heterozygote detection is often used in genetic counseling and screening programs for recessive disorders such as cystic fibrosis or sickle cell anemia. By identifying heterozygotes, individuals can be informed of their carrier status and the potential risks to their offspring. This information can help them make informed decisions about family planning and reproductive options.
Various methods can be used for heterozygote detection, including polymerase chain reaction (PCR) based tests, DNA sequencing, and genetic linkage analysis. The choice of method depends on the specific gene or mutation being tested, as well as the availability and cost of the testing technology.
A heterozygote is an individual who has inherited two different alleles (versions) of a particular gene, one from each parent. This means that the individual's genotype for that gene contains both a dominant and a recessive allele. The dominant allele will be expressed phenotypically (outwardly visible), while the recessive allele may or may not have any effect on the individual's observable traits, depending on the specific gene and its function. Heterozygotes are often represented as 'Aa', where 'A' is the dominant allele and 'a' is the recessive allele.
Tay-Sachs Disease is a rare, inherited autosomal recessive disorder that affects the nervous system's functioning. It results from the deficiency of an enzyme called hexosaminidase A (Hex-A), which is necessary for breaking down gangliosides, a type of fatty substance found in nerve cells. When Hex-A is absent or insufficient, gangliosides accumulate abnormally in the nerve cells, leading to their progressive destruction and severe neurological deterioration.
The classic infantile form of Tay-Sachs Disease manifests within the first six months of life with symptoms such as loss of motor skills, seizures, paralysis, dementia, blindness, and eventually death, usually by age four. Late-onset forms of the disease also exist, which may present in childhood or adulthood with milder symptoms.
Tay-Sachs Disease is more prevalent among individuals of Ashkenazi Jewish, French Canadian, and Cajun descent. Genetic counseling and prenatal testing are recommended for couples at risk of passing on the disease.
Hexosaminidase A is an enzyme that is responsible for breaking down certain complex molecules in the body, specifically gangliosides. This enzyme is composed of two subunits, alpha and beta, which are encoded by the genes HEXA and HEXB, respectively.
Deficiency or mutation in the HEXA gene can lead to a genetic disorder called Tay-Sachs disease, which is characterized by an accumulation of gangliosides in the nerve cells, leading to progressive neurological degeneration. The function of hexosaminidase A is to break down these gangliosides into simpler molecules that can be eliminated from the body. Without sufficient levels of this enzyme, the gangliosides build up and cause damage to the nervous system.
An encyclopedia is a comprehensive reference work containing articles on various topics, usually arranged in alphabetical order. In the context of medicine, a medical encyclopedia is a collection of articles that provide information about a wide range of medical topics, including diseases and conditions, treatments, tests, procedures, and anatomy and physiology. Medical encyclopedias may be published in print or electronic formats and are often used as a starting point for researching medical topics. They can provide reliable and accurate information on medical subjects, making them useful resources for healthcare professionals, students, and patients alike. Some well-known examples of medical encyclopedias include the Merck Manual and the Stedman's Medical Dictionary.
Beta-N-Acetylhexosaminidases are a group of enzymes that play a role in the breakdown and recycling of complex carbohydrates in the body. Specifically, they help to break down gangliosides, which are a type of molecule found in cell membranes.
There are several different isoforms of beta-N-Acetylhexosaminidases, including A, B, and S. These isoforms are formed by different combinations of subunits, which can affect their activity and substrate specificity.
Mutations in the genes that encode for these enzymes can lead to a variety of genetic disorders, including Tay-Sachs disease and Sandhoff disease. These conditions are characterized by an accumulation of gangliosides in the brain, which can cause progressive neurological deterioration and death.
Treatment for these conditions typically involves managing symptoms and providing supportive care, as there is currently no cure. Enzyme replacement therapy has been explored as a potential treatment option, but its effectiveness varies depending on the specific disorder and the age of the patient.
Nervous system diseases, also known as neurological disorders, refer to a group of conditions that affect the nervous system, which includes the brain, spinal cord, nerves, and muscles. These diseases can affect various functions of the body, such as movement, sensation, cognition, and behavior. They can be caused by genetics, infections, injuries, degeneration, or tumors. Examples of nervous system diseases include Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, migraine, stroke, and neuroinfections like meningitis and encephalitis. The symptoms and severity of these disorders can vary widely, ranging from mild to severe and debilitating.
Lipidoses are a group of genetic disorders characterized by abnormal accumulation of lipids (fats or fat-like substances) in various tissues and cells of the body due to defects in lipid metabolism. These disorders include conditions such as Gaucher's disease, Tay-Sachs disease, Niemann-Pick disease, Fabry disease, and Wolman disease, among others. The accumulation of lipids can lead to progressive damage in multiple organs, resulting in a range of symptoms and health complications. Early diagnosis and management are essential for improving the quality of life and prognosis of affected individuals.
I'm sorry for any confusion, but "Jews" is not a medical term. It is a term used to describe a group of people who share cultural, religious, and ethnic heritage. The Jewish people originated from the ancient kingdoms of Israel and Judah. They are bound together by their religion, Judaism, which is based on the Torah, or the five books of Moses.
If you have any medical questions or terms that you would like defined, I'd be happy to help!
Genomics is the scientific study of genes and their functions. It involves the sequencing and analysis of an organism's genome, which is its complete set of DNA, including all of its genes. Genomics also includes the study of how genes interact with each other and with the environment. This field of study can provide important insights into the genetic basis of diseases and can lead to the development of new diagnostic tools and treatments.
A "periodical" in the context of medicine typically refers to a type of publication that is issued regularly, such as on a monthly or quarterly basis. These publications include peer-reviewed journals, magazines, and newsletters that focus on medical research, education, and practice. They may contain original research articles, review articles, case reports, editorials, letters to the editor, and other types of content related to medical science and clinical practice.
As a "Topic," periodicals in medicine encompass various aspects such as their role in disseminating new knowledge, their impact on clinical decision-making, their quality control measures, and their ethical considerations. Medical periodicals serve as a crucial resource for healthcare professionals, researchers, students, and other stakeholders to stay updated on the latest developments in their field and to share their findings with others.
The Journal Impact Factor (JIF) is a measure of the frequency with which the "average article" in a journal has been cited in a particular year. It is calculated by dividing the number of current year citations to the source items published in that journal during the previous two years. For example, if a journal has an Impact Factor of 3 in 2020, that means articles published in 2018 and 2019 were cited 3 times on average in 2020. It is used to gauge the importance or rank of a journal by comparing the times it's articles are cited relative to other journals in the field. However, it has been criticized for various limitations such as being manipulated by editors and not reflecting the quality of individual articles.
"Access to information," in a medical context, refers to the ability of individuals, patients, healthcare providers, and researchers to obtain, request, and disseminate health-related data, records, research findings, and other important information. This includes access to personal medical records, clinical trial results, evidence-based practices, and public health statistics.
Promoting access to information is crucial for informed decision-making, ensuring transparency, advancing medical research, improving patient care, and enhancing overall healthcare system performance. Various laws, regulations, and policies at the local, national, and international levels aim to protect and facilitate access to information while balancing privacy concerns, data security, and intellectual property rights.
A plant genome refers to the complete set of genetic material or DNA present in the cells of a plant. It contains all the hereditary information necessary for the development and functioning of the plant, including its structural and functional characteristics. The plant genome includes both coding regions that contain instructions for producing proteins and non-coding regions that have various regulatory functions.
The plant genome is composed of several types of DNA molecules, including chromosomes, which are located in the nucleus of the cell. Each chromosome contains one or more genes, which are segments of DNA that code for specific proteins or RNA molecules. Plants typically have multiple sets of chromosomes, with each set containing a complete copy of the genome.
The study of plant genomes is an active area of research in modern biology, with important applications in areas such as crop improvement, evolutionary biology, and medical research. Advances in DNA sequencing technologies have made it possible to determine the complete sequences of many plant genomes, providing valuable insights into their structure, function, and evolution.
I'm sorry for any confusion, but "publishing" is not a term that has a medical definition. Publishing typically refers to the process of preparing and disseminating information, such as books, journals, or articles, to the public or a specific audience. It could involve both print and digital media. If you have any questions related to medicine or healthcare, I'd be happy to try to help answer those!
Genetically modified plants (GMPs) are plants that have had their DNA altered through genetic engineering techniques to exhibit desired traits. These modifications can be made to enhance certain characteristics such as increased resistance to pests, improved tolerance to environmental stresses like drought or salinity, or enhanced nutritional content. The process often involves introducing genes from other organisms, such as bacteria or viruses, into the plant's genome. Examples of GMPs include Bt cotton, which has a gene from the bacterium Bacillus thuringiensis that makes it resistant to certain pests, and golden rice, which is engineered to contain higher levels of beta-carotene, a precursor to vitamin A. It's important to note that genetically modified plants are subject to rigorous testing and regulation to ensure their safety for human consumption and environmental impact before they are approved for commercial use.