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Short-stature Homeobox Gene
The short-stature homeobox gene (SHOX), also known as short-stature-homeobox-containing gene, is a gene located on both the X and Y chromosomes, which is associated with short stature in humans if mutated or present in only one copy (haploinsufficiency). Pathology SHOX was first found during a search for the cause of short stature in women with Turner syndrome, where there is loss of genetic material from the X chromosome, typically by loss of one entire X chromosome. Since its discovery, the gene has been found to play a role in idiopathic short stature, Léri-Weill dyschondrosteosis, and Langer mesomelic dysplasia. Gene dosage effects of extra copies of SHOX may be a cause of the increased stature seen in other sex chromosome aneuploidy conditions such as triple X, XYY, Klinefelter, XXYY and similar syndromes. Genetics and function SHOX is composed of 6 different exons and is located in the pseudoautosomal region 1 (PAR1) of the X chromosome (Xp22.33) and Y chromoso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of Gene product, RNA or protein from a gene), DNA is first transcription (biology), copied into RNA. RNA can be non-coding RNA, directly functional or be the intermediate protein biosynthesis, template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of the population (biology), population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triple X Syndrome
Trisomy X, also known as triple X syndrome and characterized by the karyotype 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 females, but is rarely diagnosed; fewer than 10% of those with the condition know they have it. Those who have symptoms can have learning disabilities, mild dysmorphic features such as hypertelorism (wide-spaced eyes) and clinodactyly (incurved little fingers), early menopause, and increased height. As the symptoms of trisomy X are often not serious enough to prompt a karyotype test, many cases of trisomy X are diagnosed before birth via prenatal screening tests such as amniocentesis. Most females with trisomy X live normal lives, although their socioeconomic status is reduced compared to the general population. Trisomy X occurs via a process called nondisjunction, in which normal cell division is interrupted and produces gametes with too many or too few chromoso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genes On Human Chromosome X
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of RNA or protein from a gene), DNA is first copied into RNA. RNA can be directly functional or be the intermediate template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of the population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype of the individual. Most biological traits occur under the combined influence of polygenes (a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homeobox
A homeobox is a Nucleic acid sequence, DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. Mutations in a homeobox may change large-scale anatomical features of the full-grown organism. Homeoboxes are found within genes that are involved in the regulation of patterns of anatomical development (morphogenesis) in animals, fungus, fungi, plants, and numerous single cell eukaryotes. Homeobox genes encode homeodomain protein products that are transcription factors sharing a characteristic protein fold structure that binds DNA to regulate expression of target genes. Homeodomain proteins regulate gene expression and cell differentiation during early embryonic development, thus mutations in homeobox genes can cause developmental disorders. Homeosis is a term coined by William Bateson to describe the outright replacement of a discrete body part with another body part, e.g. antennapedia—replacement of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-inactivation
X-inactivation (also called Lyonization, after English geneticist Mary Lyon) is a process by which one of the copies of the X chromosome is inactivated in therian female mammals. The inactive X chromosome is silenced by being packaged into a transcriptionally inactive structure called heterochromatin. As nearly all female mammals have two X chromosomes, X-inactivation prevents them from having twice as many X chromosome gene products as males, who only possess a single copy of the X chromosome (see dosage compensation). The choice of which X chromosome will be inactivated in a particular embryonic cell is random in placental mammals such as humans, but once an X chromosome is inactivated it will remain inactive throughout the lifetime of the cell and its descendants in the organism (its cell line). The result is that the choice of inactivated X chromosome in all the cells of the organism is a random distribution, often with about half the cells having the paternal X chrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudoautosomal Region
The pseudoautosomal regions or PARs are Homology (biology), homologous sequences of Nucleotide, nucleotides found within the Sex chromosome, sex chromosomes of species with an XY sex-determination system, XY or ZW sex-determination system, ZW mechanism of Sex-determination system, sex determination. The pseudoautosomal regions get their name because any genes within them (so far at least 29 have been found for humans) are inherited just like any autosomal genes. In humans, these regions are referred to as PAR1 and PAR2. PAR1 comprises 2.6 Mbp of the short-arm tips of both X and Y chromosomes in humans and great apes (X and Y are 154 Mbp and 62 Mbp in total). PAR2 is at the tips of the long arms, spanning 320 kbp. The Monotreme, monotremes, including the platypus and echidna, have a multiple sex chromosome system, and consequently have 8 pseudoautosomal regions. Location The locations of the PARs within Genome Reference Consortium, GRCh38 are: The locations of the PARs within GR ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exon
An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence in RNA transcripts. In RNA splicing, introns are removed and exons are covalently joined to one another as part of generating the mature RNA. Just as the entire set of genes for a species constitutes the genome, the entire set of exons constitutes the exome. History The term ''exon'' is a shortening of the phrase ''expressed region'' and was coined by American biochemist Walter Gilbert in 1978: "The notion of the cistron... must be replaced by that of a transcription unit containing regions which will be lost from the mature messengerwhich I suggest we call introns (for intragenic regions)alternating with regions which will be expressedexons." This definition was originally made for protein-coding transcripts that are spliced before b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
XXYY Syndrome
XXYY syndrome is a sex chromosome anomaly in which males have two extra chromosomes, one X and one Y chromosome. Human cells usually contain two sex chromosomes, one from the mother and one from the father. Usually, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). The appearance of at least one Y chromosome with a properly functioning SRY gene makes a male. Therefore, humans with XXYY are genotypically male. Males with XXYY syndrome have 48 chromosomes instead of the typical 46. This is why XXYY syndrome is sometimes written as 48, XXYY syndrome or 48, XXYY. It affects an estimated one in every 18,000–40,000 male births. Signs and symptoms Very frequent signs and symptoms of this condition include the following: Cause 48,XXYY syndrome is a condition related to the X and Y chromosomes (the sex chromosomes). People normally have 46 chromosomes in each cell. Two of the 46 chromosomes, known as X and Y, are called sex chromosomes because they ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Klinefelter Syndrome
Klinefelter syndrome (KS), also known as 47,XXY, is a chromosome anomaly where a male has an extra X chromosome. These complications commonly include infertility and small, poorly functioning testicles (if present). These symptoms are often noticed only at puberty, although this is one of the most common chromosomal disorders. The birth prevalence of KS in the State of Victoria, Australia was estimated to be 223 per 100,000 males. It is named after American endocrinologist Harry Klinefelter, who identified the condition in the 1940s, along with his colleagues at Massachusetts General Hospital. The syndrome is defined by the presence of at least one extra X chromosome in addition to a Y chromosome, yielding a total of 47 or more chromosomes rather than the usual 46. Klinefelter syndrome occurs randomly. The extra X chromosome comes from the father and mother nearly equally. An older mother may have a slightly increased risk of a child with KS. The syndrome is diagnosed by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
XYY Syndrome
XYY syndrome, also known as Jacobs syndrome, is an aneuploid genetic condition in which a male has an extra Y chromosome. There are usually few symptoms. These may include being taller than average and an increased risk of learning disabilities. The person is generally otherwise normal, including typical rates of fertility. The condition is generally not inherited but rather occurs as a result of a random event during sperm development. Diagnosis is by a chromosomal analysis, but most of those affected are not diagnosed within their lifetime. There are 47 chromosomes, instead of the usual 46, giving a 47,XYY karyotype. Treatment may include speech therapy or extra help with schoolwork, and outcomes are generally positive. The condition occurs in about 1 in 1,000 male births. Many people with the condition are unaware that they have it. The condition was first described in 1961. Signs and symptoms Physical traits People with the 47,XYY karyotype have an increased growth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aneuploidy
Aneuploidy is the presence of an abnormal number of chromosomes in a cell (biology), cell, for example a human somatic (biology), somatic cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more ploidy#Haploid and monoploid, complete sets of chromosomes. A cell with any number of complete chromosome sets is called a ''ploidy#Euploid, euploid'' cell. An extra or missing chromosome is a common cause of some genetic disorders. Some cancer cells also have abnormal numbers of chromosomes. About 68% of human solid tumors are aneuploid. Aneuploidy originates during cell division when the chromosomes do not separate properly between the two cells (nondisjunction). Most cases of aneuploidy in the autosomes result in miscarriage, and the most common extra autosomal chromosomes among live births are Down syndrome, 21, Edwards syndrome, 18 and Patau syndrome, 13. Chromosome abnormality, Chromosome abnormalities are detected in 1 of 160 live huma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X Chromosome
The X chromosome is one of the two sex chromosomes in many organisms, including mammals, and is found in both males and females. It is a part of the XY sex-determination system and XO sex-determination system. The X chromosome was named for its unique properties by early researchers, which resulted in the naming of its counterpart Y chromosome, for the next letter in the alphabet, following its subsequent discovery. Discovery It was first noted that the X chromosome was special in 1890 by Hermann Henking in Leipzig. Henking was studying the testicles of '' Pyrrhocoris'' and noticed that one chromosome did not take part in meiosis. Chromosomes are so named because of their ability to take up staining (''chroma'' in Greek means ''color''). Although the X chromosome could be stained just as well as the others, Henking was unsure whether it was a different class of the object and consequently named it ''X element'', which later became X chromosome after it was established that it w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
