- Pseudoautosomal region
The pseudoautosomal regions, PAR1 and PAR3 are homologous sequences of
nucleotide s on the X andY chromosome sThe pseudoautosomal regions get their name because any genes located within them (so far at least 29 have been found) [Blaschke RJ, Rappold G (2006). The pseudoautosomal regions, SHOX and disease. "Curr Opin Genet Dev". Jun; 16:233-9. PMID 16650979] are inherited just like any
autosomal genes.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 over 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 s to pair and properly segregate duringmeiosis in males.Pathology
Pairing (
synapsis ) of the X and Y chromosomes and crossing over (recombination ) 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 ormutation ) 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 only gene that has so far been shown to be associated with disorders in humans, but all pseudoautosomal genes escapeX-inactivation and are therefore candidates for havinggene dosage effects in sex chromosomeaneuploidy conditions (45,X ,47,XXX ,47,XXY ,47,XYY , etc.).ee also
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Interleukin-3 receptor References
External links
*, Gene|PABY
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