Pseudoautosomal region 4629978 201618742 2008-03-28T17:33:05Z 134.129.56.144 The '''pseudoautosomal regions''', '''PAR1''' and '''PAR3''' are [[Homology (biology)|homologous]] sequences of [[nucleotide]]s on the [[X chromosome|X]] and [[Y chromosome]]s The pseudoautosomal regions get their name because any genes located within them (so far at least 29 have been found)<ref>Blaschke RJ, Rappold G (2006). The pseudoautosomal regions, SHOX and disease. ''Curr Opin Genet Dev''. Jun; '''16''':233-9. PMID 16650979</ref> 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 during [[meiosis]] 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 [[nucleic acid hybridization|hybridization]] or [[mutation]]) 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 escape [[X-inactivation]] and are therefore candidates for having [[gene dosage]] effects in sex chromosome [[aneuploidy]] conditions ([[45,X]], [[47,XXX]], [[47,XXY]], [[47,XYY]], etc.). ==See also== * [[Interleukin-3 receptor]] ==References== {{reflist}} ==External links== * {{Gene|PABX}}, {{Gene|PABY}} [[Category:Molecular genetics]][[Category:Cytogenetics]] [[de:Pseudoautosomale Region]] [[fr:Région pseudo-autosomique]]