Pseudoautosomal region
Encyclopedia
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
sequences of nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s on the X
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
and Y chromosome
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
s.
The pseudoautosomal regions get their name because any genes located within them (so far at least 29 have been found) are inherited just like any autosomal genes. PAR1 comprises 2.6 Mbp of the short-arm tips of both X and Y chromosomes in humans and other great apes (X and Y are 155 Mbp and 59 Mbp in total). PAR2 is located at the tips of the long arms, spanning 320 kbp.
Inheritance and function
Normal male mammals have two copies of these genes: one in the pseudoautosomal region of their Y chromosome, the other in the corresponding portion of their X chromosome. Normal females also possess two copies of pseudoautosomal genes, as each of their two X chromosomes contains a pseudoautosomal region. Crossing overChromosomal crossover
Chromosomal crossover is an exchange of genetic material between homologous chromosomes. It is one of the final phases of genetic recombination, which occurs during prophase I of meiosis in a process called synapsis. Synapsis begins before the synaptonemal complex develops, and is not completed...
between the X and Y chromosomes is normally restricted to the pseudoautosomal regions; thus, pseudoautosomal genes exhibit an autosomal, rather than sex-linked, pattern of inheritance. So, females can inherit an allele originally present on the Y chromosome of their father and males can inherit an allele originally present on the X chromosome of their father.
The function of these pseudoautosomal regions is that they allow the X and Y chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s to pair and properly segregate during meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
in males.
Genes
Pseudoautosomal genes are found in two different locations: PAR1 and PAR2. These are believed to have evolved independently.PAR1
- pseudoautosomal PAR1
- ASMT
- ASMTLASMTLN-acetylserotonin O-methyltransferase-like protein is an enzyme that in humans is encoded by the ASMTL gene.-Further reading:...
- CD99CD99CD99 antigen also known as MIC2 or single-chain type-1 glycoprotein is a protein that in humans is encoded by the CD99 gene. The protein has a mass of 32 kD...
- CRLF2CRLF2Cytokine receptor-like factor 2 is a protein that in humans is encoded by the CRLF2 gene.-Further reading:...
- CSF2RA
- SFRS17ASFRS17ASplicing factor, arginine/serine-rich 17A is a protein that in humans is encoded by the SFRS17A gene.-Further reading:...
- DHRSXY
- GTPBP6GTPBP6GTP binding protein 6 also known as GTPBP6 is a protein which in humans is encoded by the pseudoautosomal GTPBP6 gene.- Clinical significance :...
- IL3RAIL3RAInterleukin 3 receptor, alpha , also known as CD123 , is a human gene.-Interactions:IL3RA has been shown to interact with Interleukin 3.-External links:...
- P2RY8P2RY8P2Y purinoceptor 8 is a protein that in humans is encoded by the P2RY8 gene.-Further reading:...
- PLCXD1PLCXD1Phosphatidylinositol-specific phospholipase C, X domain containing 1 also known as PLCXD1 is an enzyme which in humans is encoded by the PLCXD1 pseudoautosomal gene....
- PPP2R3BPPP2R3BSerine/threonine-protein phosphatase 2A regulatory subunit B subunit beta is an enzyme that in humans is encoded by the PPP2R3B gene.-Interactions:PPP2R3B has been shown to interact with PPP2R1B, PPP2R1A, CDC6 and PPP2CA.-Further reading:...
- SHOXShoxShox is an arcade, rally game, it is available on the PlayStation 2 console in the USA and Europe.-Gameplay:Shox is based around the concept of a shockwave that appears in front of the player's car if they successfully pass, within the time limit, through three points on a track...
- SLC25A6SLC25A6ADP/ATP translocase 3 also known as solute carrier family 25 member 6 is a protein that in humans is encoded by the SLC25A6 gene.Identical copies of this gene reside on the pseudoautosomal regions of the X and Y chromosomes....
- XGXg antigen systemThe XG antigen is a red blood cell surface antigen discovered in 1962.The PBDX gene that encodes the antigen is located on the short arm of the X chromosome. Since males normally have one X chromosome they are considered hemizygotes...
- ZBED1ZBED1Zinc finger BED domain-containing protein 1 is a protein that in humans is encoded by the ZBED1 gene.-Further reading:...
In mice
MICE
-Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...
, some PAR1 genes have transferred to autosome
Autosome
An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y...
s.
PAR2
- pseudoautosomal PAR2
- SPRY3SPRY3Protein sprouty homolog 3 is a protein that in humans is encoded by the SPRY3 gene.-Further reading:...
- SYBL1SYBL1Vesicle-associated membrane protein 7 is a protein that in humans is encoded by the VAMP7 gene.- Function :VAMP-7 is a transmembrane protein that is a member of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor family...
- IL9R
- CXYorf1, which is now mapped to the pseudogenePseudogenePseudogenes are dysfunctional relatives of known genes that have lost their protein-coding ability or are otherwise no longer expressed in the cell...
"WASH6P", but is of interest due to its proximity to the telomereTelomereA telomere is a region of repetitive DNA sequences at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Its name is derived from the Greek nouns telos "end" and merοs "part"...
.
- SPRY3
Pathology
Pairing (synapsisSynapsis
Synapsis is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I. When homologous chromosomes synapse, their ends are...
) of the X and Y chromosomes and crossing over (recombination
Genetic recombination
Genetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method...
) between their pseudoautosomal regions appear to be necessary for the normal progression of male meiosis. Thus, those cells in which X-Y recombination does not occur will fail to complete meiosis. Structural and/or genetic dissimilarity (due to hybridization or mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
) between the pseudoautosomal regions of the X and Y chromosomes can disrupt pairing and recombination, and consequently cause male infertility.
The SHOX gene in the PAR1 region is the gene most commonly associated with and well understood with regards to disorders in humans, but all pseudoautosomal genes escape X-inactivation
X-inactivation
X-inactivation is a process by which one of the two copies of the X chromosome present in female mammals is inactivated. The inactive X chromosome is silenced by packaging into transcriptionally inactive heterochromatin...
and are therefore candidates for having gene dosage
Gene dosage
Gene dosage is the number of copies of a gene present in a cell or nucleus. An increase in gene dosage can cause higher levels of gene product if the gene is not subject to regulation from elsewhere in the body....
effects in sex chromosome aneuploidy
Aneuploidy
Aneuploidy is an abnormal number of chromosomes, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorders . Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division when the chromosomes do not separate...
conditions (45,X, 47,XXX, 47,XXY, 47,XYY, etc.).
Deletions have also been associated with Léri-Weill dyschondrosteosis
Léri-Weill dyschondrosteosis
Léri-Weill dyschondrosteosis or LWD is a rare genetic disorder which results in dwarfism with short forearms and legs and a particular deformity of the forearms .-Causes:...
and Madelung's deformity
Madelung's deformity
Madelung's deformity is usually characterized by malformed wrists and wrist bones and short stature and is often associated with Léri-Weill dyschondrosteosis...
.