Y chromosome, the smallest chromosome of the karyotpe, is one of the two sex chromosomes. In 1905, Nettie Stevens identified that Y chromosome is a sex-determining chromosome, while conducting one study of the mealworm Tenebrio molitor. He also proposed that chromosomes always existed in pairs. In 1890 Hermann Henking discovered that Y chromosome was the pair of the X chromosome. All chromosomes normally appear to take on a well defined shape during mitosis when seen under microscope. This shape is vaguely X-shaped for all chromosomes. Interestingly, the Y chromosome looks like the English alphabet Y during mitosis, due to merging of the two very short branches (Bainbridge, 2003). Every species organism consists of different set of
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The rest of Y chromosome (~95%) is known as non recombining region or male specific region (Singh A R et al., 2005). As the Y chromosome is present only in males, the genes on this chromosome tend to be involved in male sex determination and development. It also consists of gene SRY which triggers testis determination and male development and contains genes specific for spermatogenesis. Loss of SRY gene from Y chromosome results in XY individuals (normally male) having female characteristics (Swyer syndrome). Y chromosome is present in different size and shape in different species. In cattle (Bos taurus, BTA) it is a small submetacentric, in zebu (Bos indicus, BIN) it is a small acrocentric with visible small p-arms, in river buffalo (Bubalus bubalis, BBU) it is a small acrocentric, while in both sheep (Ovis aries, OAR) and goat (Capra hircus, CHI) it is a very small metacentric (Moe et al., 2005).
Y chromosome and infertility
Tiepolo and Zuffardi (1976) first reported the involvement of Y chromosome in male infertility (Vereb et al., 1997). It was reported that during the course of evolution that Y chromosome acquired a large number of testes specific genes responsible for spermatogenesis and any deletion in these genes results in infertility (Singh A R et al., 2005). The microdeletions at Yq11 shown by molecular studies analysis represent etiological factor with idiopathic