Chapter 23 Notes: Evolution of Genetic Systems: Figure WN23.11 - The evolution of the human Y chromosome can be traced by comparing its sequence with the X chromosome.

Figure WN23.11 - The evolution of the human Y chromosome can be traced by comparing its sequence with the X chromosome.

Figure WN23.11. The evolution of the human Y chromosome can be traced by comparing its sequence with the X chromosome. (A) Divergence at synonymous sites (K_s) for 31 X-Y gene pairs plotted against the order of the genes on the X chromosome. Gene pairs fall into four classes, which correspond to four events in which the nonrecombining region of the Y expanded to include more genes. Two genes (TGIF2LY, PCDH11Y; pink) show unusually low divergence and are thought to have recently translocated from the X. (B) Inferred history of the human Y chromosome. Arrows indicate successive expansions of the male-specific region (red). The pseudoautosomal region, in which X and Y recombine freely, is shown in blue. About 80–130 Mya, a translocation from an autosome increased the size of the pseudoautosomal region (blue). The recent translocation of the PCDH11Y gene from X to Y is shown in green. (A, Redrawn from Fig. 7 of Skaletsky et al. 2003. B, Redrawn from Fig. 3 of Lahn et al. 2001.)

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