Understanding the Y Chromosome

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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 chromosome with one set of sex determining chromosome.
The X and Y chromosomes are thought to have evolved from a pair of identical chromosomes, known as autosome. The mammalian males are heterogametic (produces X and Y chromosome bearing sperms in equal proportions), and the females are heterogametic (all female gametes are X bearing). It was found that Y chromosome has high repetitive DNA sequence content which consists of pseudogenes and does not have any function (Delbridge et al., 1999). In males, Y chromosome consists of SRY gene which triggers embryo development as male. Y chromosome is the smallest chromosome consists of 2-3% of haploid genome and contains between 70 and 200 genes (Quintana-Murci et al., 2001). Y chromosome consists of 2 arms- short arm (Yp) and long arm (Yq). These arms consist of 2 pseudoautosomal regions PAR1 and PAR2 which recombine with their homologous regions on X chromosome. The absence of recombination makes genetic mapping of the Y-specific region impossible, and the ...

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