Prader-Willi Syndrome: An autosomal dominant disorder caused by deletion of the proximal long arm of the paternal chromosome 15 (15q11-q13) or by inheritance of both of the pair of chromosomes 15 from the mother (UNIPARENTAL DISOMY) which are imprinted (GENETIC IMPRINTING) and hence silenced. Clinical manifestations include MENTAL RETARDATION; MUSCULAR HYPOTONIA; HYPERPHAGIA; OBESITY; short stature; HYPOGONADISM; STRABISMUS; and HYPERSOMNOLENCE. (Menkes, Textbook of Child Neurology, 5th ed, p229)Chromosomes, Human, Pair 15: A specific pair of GROUP D CHROMOSOMES of the human chromosome classification.Angelman Syndrome: A syndrome characterized by multiple abnormalities, MENTAL RETARDATION, and movement disorders. Present usually are skull and other abnormalities, frequent infantile spasms (SPASMS, INFANTILE); easily provoked and prolonged paroxysms of laughter (hence "happy"); jerky puppetlike movements (hence "puppet"); continuous tongue protrusion; motor retardation; ATAXIA; MUSCLE HYPOTONIA; and a peculiar facies. It is associated with maternal deletions of chromosome 15q11-13 and other genetic abnormalities. (From Am J Med Genet 1998 Dec 4;80(4):385-90; Hum Mol Genet 1999 Jan;8(1):129-35)snRNP Core Proteins: The protein components that constitute the common core of small nuclear ribonucleoprotein particles. These proteins are commonly referred as Sm nuclear antigens due to their antigenic nature.Genomic Imprinting: The variable phenotypic expression of a GENE depending on whether it is of paternal or maternal origin, which is a function of the DNA METHYLATION pattern. Imprinted regions are observed to be more methylated and less transcriptionally active. (Segen, Dictionary of Modern Medicine, 1992)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).Syndrome: A characteristic symptom complex.Ribonucleoproteins, Small Nuclear: Highly conserved nuclear RNA-protein complexes that function in RNA processing in the nucleus, including pre-mRNA splicing and pre-mRNA 3'-end processing in the nucleoplasm, and pre-rRNA processing in the nucleolus (see RIBONUCLEOPROTEINS, SMALL NUCLEOLAR).Muscle Hypotonia: A diminution of the skeletal muscle tone marked by a diminished resistance to passive stretching.RNA, Small Nucleolar: Small nuclear RNAs that are involved in the processing of pre-ribosomal RNA in the nucleolus. Box C/D containing snoRNAs (U14, U15, U16, U20, U21 and U24-U63) direct site-specific methylation of various ribose moieties. Box H/ACA containing snoRNAs (E2, E3, U19, U23, and U64-U72) direct the conversion of specific uridines to pseudouridine. Site-specific cleavages resulting in the mature ribosomal RNAs are directed by snoRNAs U3, U8, U14, U22 and the snoRNA components of RNase MRP and RNase P.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.Chromosome Deletion: Actual loss of portion of a chromosome.Tooth Attrition: The wearing away of a tooth as a result of tooth-to-tooth contact, as in mastication, occurring only on the occlusal, incisal, and proximal surfaces. It is chiefly associated with aging. It is differentiated from TOOTH ABRASION (the pathologic wearing away of the tooth substance by friction, as brushing, bruxism, clenching, and other mechanical causes) and from TOOTH EROSION (the loss of substance caused by chemical action without bacterial action). (Jablonski, Dictionary of Dentistry, 1992, p86)Hyperphagia: Ingestion of a greater than optimal quantity of food.Intellectual Disability: Subnormal intellectual functioning which originates during the developmental period. This has multiple potential etiologies, including genetic defects and perinatal insults. Intelligence quotient (IQ) scores are commonly used to determine whether an individual has an intellectual disability. IQ scores between 70 and 79 are in the borderline range. Scores below 67 are in the disabled range. (from Joynt, Clinical Neurology, 1992, Ch55, p28)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.Genetic Determinism: The theory that human CHARACTER and BEHAVIOR are shaped by the GENES that comprise the individual's GENOTYPE rather than by CULTURE; ENVIRONMENT; and individual choice.Human Growth Hormone: A 191-amino acid polypeptide hormone secreted by the human adenohypophysis (PITUITARY GLAND, ANTERIOR), also known as GH or somatotropin. Synthetic growth hormone, termed somatropin, has replaced the natural form in therapeutic usage such as treatment of dwarfism in children with growth hormone deficiency.Chromosome Breakage: A type of chromosomal aberration involving DNA BREAKS. Chromosome breakage can result in CHROMOSOMAL TRANSLOCATION; CHROMOSOME INVERSION; or SEQUENCE DELETION.Theft: Unlawful act of taking property.Adrenarche: A stage of development at which the ADRENAL GLANDS undergo maturation leading to the capability of producing increasing amounts of adrenal androgens, DEHYDROEPIANDROSTERONE and ANDROSTENEDIONE. Adrenarche usually begins at about 7 or 8 years of age before the signs of PUBERTY and continues throughout puberty.Fathers: Male parents, human or animal.Albinism: General term for a number of inherited defects of amino acid metabolism in which there is a deficiency or absence of pigment in the eyes, skin, or hair.Autoantigens: Endogenous tissue constituents that have the ability to interact with AUTOANTIBODIES and cause an immune response.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.DNA Methylation: Addition of methyl groups to DNA. DNA methyltransferases (DNA methylases) perform this reaction using S-ADENOSYLMETHIONINE as the methyl group donor.Q-Sort: A personality assessment technique in which the subject or observer indicates the degree to which a standardized set of descriptive statements actually describes the subject. The term reflects "sorting" procedures occasionally used with this technique.Gonadal Disorders: Pathological processes of the OVARIES or the TESTES.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.Karyotyping: Mapping of the KARYOTYPE of a cell.Ghrelin: A 28-amino acid, acylated, orexigenic peptide that is a ligand for GROWTH HORMONE SECRETAGOGUE RECEPTORS. Ghrelin is widely expressed but primarily in the stomach in the adults. Ghrelin acts centrally to stimulate growth hormone secretion and food intake, and peripherally to regulate energy homeostasis. Its large precursor protein, known as appetite-regulating hormone or motilin-related peptide, contains ghrelin and obestatin.Hypogonadism: Condition resulting from deficient gonadal functions, such as GAMETOGENESIS and the production of GONADAL STEROID HORMONES. It is characterized by delay in GROWTH, germ cell maturation, and development of secondary sex characteristics. Hypogonadism can be due to a deficiency of GONADOTROPINS (hypogonadotropic hypogonadism) or due to primary gonadal failure (hypergonadotropic hypogonadism).