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Encyclopedia > Y chromosome

The Y chromosome is one of the sex-determining chromosomes in humans and most other mammals (the other is the X chromosome). In mammals, it contains the gene SRY, which triggers testis development, thus determining sex. Image File history File links No higher resolution available. ... A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. ... Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division. ... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin: wise man or knowing man) in the family Hominidae (the great apes). ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the production of milk in female mammary glands and by the presence of: hair, three middle ear bones used in hearing, and a neocortex region in... The X chromosome The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals (the other is the Y chromosome). ... SRY (Sex-determining Region Y) is a sex-determining gene on the Y chromosome in humans and other primates. ... The testicle (from Latin testis, meaning witness [1], plural testes) is the male generative gland in animals. ...

Contents

Overview

Most mammals have one pair of sex chromosomes in each cell. Males have one Y chromosome and one X chromosome, while females have two X chromosomes. In mammals, the Y chromosome contains the gene that triggers embryonic development as a male. This gene is SRY. Other genes (in addition to SRY) on the Y chromosomes of men and other mammals are needed for normal sperm production. SRY (Sex-determining Region Y) is a sex-determining gene on the Y chromosome in humans and other primates. ... SRY (Sex-determining Region Y) is a sex-determining gene on the Y chromosome in humans and other primates. ...


There are exceptions, however. Among humans, some men have two X's and a Y ("XXY", see Klinefelter's syndrome), or one X and two Y's (see XYY syndrome), and some women have three Xs or a single X (and no Y, "X0", see Turner syndrome). There are other exceptions in which SRY is damaged (leading to an XY female), or copied to the X (leading to an XX male). For related phenomena see Androgen insensitivity syndrome and Intersex. Not to be confused with XYY syndrome or XXX syndrome. ... Not to be confused with XXY syndrome. ... SRY (Sex-determining Region Y) is a sex-determining gene on the Y chromosome in humans and other primates. ... Swyer syndrome, or XY gonadal dysgenesis, is a type of female hypogonadism in which no functional gonads are present to induce puberty in an otherwise normal girl whose karyotype is then found to be XY. Her gonads are found to be nonfunctional streaks. ... Androgen insensitivity syndrome (AIS, or Androgen resistance syndrome) is a set of disorders of sexual differentiation that results from mutations of the gene encoding the androgen receptor. ... An intersexual is a person (or individual of any unisexual species) who is born with genitalia and/or secondary sexual characteristics of indeterminate sex, or which combine features of both sexes. ...


Many groups of organisms in addition to mammals have Y chromosomes, but these Y chromosomes do not share common ancestry with mammalian Y chromosomes. Such groups include fruit flies (Drosophila melanogaster and relatives), some other insects, some fish, some reptiles, and some plants. In fruit flies, the Y chromosome does not trigger male development. Instead, sex is determined by the number of X chromosomes. So XXY fruit flies are female, and fruit flies with a single X (X0), are male but sterile. Binomial name Drosophila melanogaster Meigen, 1830 [1] Drosophila melanogaster (from the Greek for black-bellied dew-lover) is a two-winged insect that belongs to the Diptera, the order of the flies. ...


Other organisms have mirror image sex chromosomes: the female is "XY" and the male is "XX", but by convention biologists call a "female Y" a W chromosome and the other a Z chromosome. For example, female birds, snakes, and butterflies have ZW sex chromosomes, and males have ZZ sex chromosomes. The ZW sex-determination system is a system that birds, some fishes, and some insects (including butterflies and moths) use to determine the sex of their offspring. ... Z chromosome: A sex chromosome in certain animals, such as chickens, turkeys, and moths. ...


A closely related topic is Sex determination. A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. ...


Origins and evolution

Many ectothermic vertebrates have no sex chromosomes. If they have different sexes, sex is determined environmentally rather than genetically. For some of them, especially reptiles, sex depends on the incubation temperature, others are hermaphroditic. Cold-blooded organisms, more technically known as poikilothermic, are animals that have no internal metabolic mechanism for regulating their body temperatures. ... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Subclasses Anapsida Diapsida Synonyms Reptilia Laurenti, 1768 Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane, and members of the class Sauropsida. ...


The X and Y chromosomes diverged around 300 million years ago from a pair of identical chromosomes[1], termed autosomes, when an ancestral mammal developed an allelic variation, a so-called 'sex locus' - simply possessing this allele caused the organism to be male[2] The chromosome with this allele became the Y chromosome, while the other member of the pair became the X chromosome. Over time, genes which were beneficial for males and harmful to (or had no effect on) females either developed on the Y chromosome, or were acquired through the process of translocation.[3] An autosome is a non-sex chromosome. ... For the hard rock band, see Allele (band). ... Chromosomal translocation of the 4th and 20th chromosome. ...


Recombination between the X and Y chromosomes proved harmful - it resulted in males without necessary genes formerly found on the X chromosome, and females with unnecessary or even harmful genes previously only found on the Y chromosome. As a result, genes beneficial to males accumulated near the sex-determining genes, and recombination in this region was suppressed in order to preserve this male specific region[4]. Over time, the Y chromosome changed in such a way as to inhibit the areas around the sex determining genes from recombining at all with the X chromosome. Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ...


With time, larger and larger areas became unable to recombine with the X chromosome. This caused its own problems: without recombination, the removal of harmful mutations from chromosomes becomes increasingly difficult. These harmful mutations continued to damage Y-unique genes until several finally stopped functioning and became genetic junk; this was eventually removed from the Y chromosome. In molecular biology, junk DNA is a collective label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified. ...


As a result of this process 95% of the human Y chromosome is unable to recombine, the chromosome itself contains only 86 working genes;[5] compare this to close to 1000 working genes on the X chromosome. In some animals, Y degradation is even more severe. The 10-12 Mb dunnart Y chromosome, with only four characterised genes; among them the SRY gene, is the smallest known mammalian Y chromosome. [6] Dunnarts are furry narrow-footed marsupials the size of a mouse. ... SRY (Sex-determining Region Y) is a sex-determining gene on the Y chromosome in humans and other primates. ...


Gene conversion

In 2003, researchers from MIT discovered another process which may slow down the process of degradation. They found that human Y chromosome is able to "recombine" with itself, using palindrome base pair sequences.[7] Such a "recombination" is called gene conversion or "recombinational loss of heterozygosity" RecLOH. 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Mapúa Institute of Technology (MIT, MapúaTech or simply Mapúa) is a private, non-sectarian, Filipino tertiary institute located in Intramuros, Manila. ... Look up Palindrome in Wiktionary, the free dictionary. ... Base pairs, of a DNA molecule. ... Gene conversion is a phenomenon which occurs during meiotic division. ... RecLOH is a term in genetics that is an abbreviation for Recombinational Loss of Heterozygosity. This is a type of mutation which occurs with DNA during recombination. ...


In the case of the Y chromosomes, the palindromes are not junk DNA; these strings of bases contain functioning genes important for male fertility. Most of the sequence pairs are greater than 99.97% identical. The extensive use of gene conversion may play a role in the ability of the Y chromosome to edit out genetic mistakes and maintain the integrity of the relatively few genes it carries. Look up Palindrome in Wiktionary, the free dictionary. ... In molecular biology, junk DNA is a collective label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified. ...


Findings were confirmed by comparing similar regions of the Y chromosome in humans to the Y chromosomes of chimpanzees, bonobos and gorillas. The comparison demonstrated that the same phenomenon of gene conversion appeared to be at work more than 5 million years ago, when humans and the non-human primates diverged from each other. Type species Simia troglodytes Blumenbach, 1775 distribution of Species Pan troglodytes Pan paniscus Chimpanzee, often shortened to chimp, is the common name for the two extant species in the genus Pan. ... For other uses, see Bonobo (disambiguation). ... Type species Troglodytes gorilla Savage, 1847 distribution of Gorilla Species Gorilla gorilla Gorilla beringei The gorilla, the largest of the living primates, is a ground-dwelling omnivore that inhabits the forests of Africa. ...


This recombination phenomenon RecLOH is also observed in Genetic Genealogy when multicopy Y-STR markers located at adjacent palindromic arms change from different repeat counts to twin alleles of equal length. Often 2, 3 or more Y-STR markers are involved in the same recombinational event and change to twin alleles at once. RecLOH is a term in genetics that is an abbreviation for Recombinational Loss of Heterozygosity. This is a type of mutation which occurs with DNA during recombination. ... A Y-STR is a short tandem repeat (STR) on the Y chromosome. ...


Future evolution

After only an SRY (or other sex-determining) gene remains from the whole Y chromosome, there are the following possibilities:

  • The gene is connected to X chromosome or some autosome, making it the new Y chromosome. The whole process starts again. This has happened with two species of mole vole (Ellobius tancrei and E. lutescens). In one species, both sexes have unpaired X chromosomes; in the other, both females and males have XX.
  • Part of some autosome is connected to both the X and Y chromosomes. This happened with one species of Drosophila.

An autosome is a non-sex chromosome. ... Genera see text Arvicolinae is a subfamily of rodents that includes the voles, lemmings, and muskrats. ... Binomial name Blasius, 1884 The Zaisan Mole Vole (Ellobius tancrei) is a species of rodent in the Muridae family. ... Type Species Musca funebris Fabricius, 1787 Drosophila is a genus of small flies whose members are often called small fruit flies, or more appropriately vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies. ...

Human Y chromosome

In humans, the Y chromosome spans 58 million base pairs (the building blocks of DNA) and represents approximately 0.38% of the total DNA in a human cell. The human Y chromosome contains 78 genes, which code for only 23 distinct proteins. This relationship is typical in that most species' Y chromosomes contain the fewest genes of any of the chromosomes.[citation needed] Base pairs, of a DNA molecule. ... The structure of part of a DNA double helix Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions for the development and function of living organisms. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ...


Because the Y chromosome changes relatively slowly over time and is only passed along the direct male line, it may be used to trace paternal lineage. It is the cause of the fewest number of known genetic diseases in humans (44 in total).[citation needed]


The human Y chromosome is unable to recombine with the X chromosome, except for small pieces of pseudoautosomal regions at the telomeres (which comprise about 5% of the chromosome's length). These regions are relics of ancient homology between the X and Y chromosomes. About 56, or 72%, of the Y chromosome genes are in this area; as a result, these genes are common between both sex chromosomes.[citation needed] A telomere is a region of highly repetitive DNA at the end of a chromosome that functions as a disposable buffer. ... In biology, homology is any similarity between structures that is due to their shared ancestry. ...


Genes

  • AMELY (amelogenin,Y-chromosomal)
  • ANT3Y (adenine nucleotide translocator-3 on the Y)
  • ASMTY (which stands for acetylserotonin methyltransferase)
  • AZF1 (azoospermia factor 1)
  • AZF2 (azoospermia factor 2)
  • BPY2 (basic protein on the Y chromosome)
  • CSF2RY (granulocyte-macrophage colony-stimulating factor receptor, alpha subunit on the Y chromosome)
  • DAZ (deleted in azoospermia)
  • IL3RAY (interleukin-3 receptor)
  • PRKY (protein kinase, Y-linked)
  • RBM1 (RNA binding motif protein, Y chromosome, family 1, member A1)
  • RBM2 (RNA binding motif protein 2)
  • SRY (sex-determining region)
  • TDF (testis determining factor)
  • TSPY (testis-specific protein)
  • UTY (ubiquitously transcribed TPR gene on Y chromosome)
  • ZFY (zinc finger protein)

Amelogenin is a gene-specific, low-molecular-weight protein found in tooth enamel, and it belongs to a family of extracellular matrix (ECM) proteins. ... Adenine nucleotide translocator is a mitochondrial protein. ... AZF is an acronym for a region on the human male Y chromosome called the AZoospermia Factor. ... Azoospermia is the medical condition of a man not having any measurable level of sperm in his semen. ... Interleukins are a group of cytokines that were first seen to be expressed by white blood cells (leukocytes, hence the -leukin) as a means of communication (inter-). The name is sort of a relic though; it has since been found that interleukins are produced by a wide variety of bodily... Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... SRY (Sex-determining Region Y) is a sex-determining gene on the Y chromosome in humans and other primates. ... Testis-determining factor (TDF) is a general term for the gene (or product thereof) that results in maleness in humans and some other species. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... A zinc finger protein is a DNA-binding protein domain comprised of three zinc fingers. ...

Chromosome-linked diseases

No vital genes reside only on the Y chromosome, since 50% of humans (females) do not have Y chromosomes. The only well-defined human disease linked to a defect on the Y chromosome is defective testicular development (due to deletion or deleterious mutation of SRY). This results in the person presenting a female phenotype even though that person possesses an XY karyotype (i.e., is born with female-like genitalia). The lack of the second X results in infertility. Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... Karyogram of human male using Giemsa staining. ...


However, it is possible for an abnormal number (aneuploidy) of Y chromosomes to result in problems.


47,XYY syndrome is caused by the presence of a single extra copy of the Y chromosome in each of a male's cells. Males with 47,XYY syndrome have one X chromosome and two Y chromosomes, for a total of 47 chromosomes per cell. Researchers have repeatedly found that an extra copy of the Y chromosome is associated with tall stature and/or learning problems in some boys and men, but the magnitude of the effects are variable and often minimal or undetectable. When chromosome surveys were first done in the 1960s, it was reported that a higher than expected number of men in prisons were found to have an extra Y chromosome, so that for a while it was thought to predispose a boy to antisocial behavior (and was dubbed the "criminal karyotype"). Better population surveys have since demonstrated that the association was simply that boys and men with learning problems are more likely statistically to spend time in prison and that there is no other independent statistical association with extra Y. The "criminal karyotype" concept is inaccurate and obsolete. XYY, or XYY syndrome, is a trisomy of the sex chromosomes in which a human male receives an extra Y chromosome in each cell, hence having a karyotype of 47,XYY. Effects Physical traits XYY syndrome typically causes no unusual physical features or medical problems. ...


Greater degrees of Y chromosome polysomy (having more than one extra copy of the Y chromosome in every cell, e.g., XYYYY) are rare. The extra genetic material in these cases can lead to skeletal abnormalities, decreased IQ, and delayed development, but the severity features of these conditions are variable.


There are also problems that arise from having an incomplete Y chromosome: the usual karyotype in these cases is 46X, plus a fragment of Y. This usually results in defective testicular development, such that the infant may or may not have fully formed male genitalia internally or externally. The full range of ambiguity of structure may occur, especially if mosaicism is present. When the Y fragment is minimal and nonfunctional, the child usually is a girl with the features of Turner syndrome or mixed gonadal dysgenesis but a risk of malignancy. Mixed gonadal dysgenesis refers to a condition of abnormal and asymmetrical gonadal development leading to a disturbed sex differentiation. ...


Klinefelter's syndrome (47, XXY) is not an aneuploidy of the Y chromosome, but a condition of having an extra X chromosome. It usually results in defective postnatal testicular function, but as the extra X does not seem to be due to direct interference with expression of Y genes, and the mechanism is not fully understood. Not to be confused with XYY syndrome or XXX syndrome. ...


Genetic genealogy

In human genetic genealogy (the application of genetics to traditional genealogy) use of the information contained in the Y chromosome is of particular interest since, unlike other genes, the Y chromosome is passed exclusively from father to son.[8] Genetic genealogy is the application of genetics to traditional genealogy. ... DNA, the molecular basis for inheritance. ... Genealogy is the study and tracing of family pedigrees. ...


See also

In human genetics, Human Y-chromosome DNA haplogroups are haplogroups defined by differences in the non-recombining portions of DNA from the Y chromosome (called Y-DNA). ... DYS is short for DNA Y-chromosome Segment, and is used to designate a segment of DNA on the Y chromosome where a sequence of nucleotides repeats. ... The following DYS markers are commonly tested in genealogical DNA testing. ... In human genetics, Y-chromosomal Adam (Y-mrca) is the male counterpart to mitochondrial Eve: the most recent common ancestor from whom all male human Y chromosomes are descended. ... Y-chromosomal Aaron is the name given to the hypothesised most recent common ancestor of many of the patrilineal Jewish priestly caste known as Kohanim (singular Kohen, Cohen, or Kohane). ... Genetic genealogy is the application of genetics to traditional genealogy. ... // A genealogical DNA test involves examining the nucleotides at specific locations on a persons DNA. The tests results are meant to have no informative medical value and do not determine specific genetic diseases or disorders (see possible exceptions in Medical information below); they are intended only for use in... A Y-STR is a short tandem repeat (STR) on the Y chromosome. ... In mammals, Y-linkage refers to when a phenotypic trait is determined by an allele (or gene) on the Y chromosome. ... The X chromosome The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals (the other is the Y chromosome). ...

References

  1. ^ Lahn B, Page D (1999). "Four evolutionary strata on the human X chromosome". Science 286 (5441): 964-7. PMID 10542153. 
  2. ^ Graves J.A.M. (2006). "Sex chromosome specialization and degeneration in mammals". Cell 124 (5): 901-14. PMID 16530039. 
  3. ^ Graves J.A.M., Koina E., Sankovic N. (2006). "How the gene content of human sex chromosomes evolved". Curr Opin Genet Dev 16 (3): 219-24. PMID 16650758. 
  4. ^ Graves J.A.M. (2006). "Sex chromosome specialization and degeneration in mammals". Cell 124 (5): 901-14. PMID 16530039. 
  5. ^ Ensembl Human MapView release 43 (Feb 2007). Retrieved on 2007-04-14.
  6. ^ Toder R., Wakefield M.J., Graves J.A.M. (2000). "The minimal mammalian Y chromosome - the marsupial Y as a model system". Cytogenet Cell Genet 91 (1-4): 285-92. PMID 11173870. 
  7. ^ Rozen S, Skaletsky H, Marszalek J, Minx P, Cordum H, Waterston R, Wilson R, Page D (2003). "Abundant gene conversion between arms of palindromes in human and ape Y chromosomes". Nature 423 (6942): 873-6. PMID 12815433. 
  8. ^ See www.smgf.org for more information.
  • Skaletsky, H.S., et al. (2003) The male-specific region of the human Y chromosome is a mosaic of discrete sequence classes. Nature, 423, 825-837
  • Rozen, S., et al. (2003) Abundant gene conversion between arms of palindromes in human and ape Y chromosomes. Nature, 423, 873-876.

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 14 is the 104th day of the year (105th in leap years) in the Gregorian calendar, with 261 days remaining. ...

External links


  Results from FactBites:
 
Y chromosome - Genetics Home Reference (784 words)
The Y chromosome is one of the two sex chromosomes in humans (the other is the X chromosome).
Genes on the Y chromosome are among the estimated 20,000 to 25,000 total genes in the human genome.
Chromosomal conditions involving the sex chromosomes often affect sex determination (whether a person has the sexual characteristics of a male or a female), sexual development, and the ability to have children (fertility).
Y Chromosome (1367 words)
The Y chromosome is one of the two sex chromosomes in humans (the other is the X chromosome).
Genes on the Y chromosome are among the estimated 20,000 to 25,000 total genes in the human genome.
Chromosomal conditions involving the sex chromosomes often affect sex determination (whether a person has the sexual characteristics of a male or a female), sexual development, and the ability to have children (fertility).
  More results at FactBites »

 
 

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