Figure 6.

History of gene conversion in the X and Y homologous chromosomal region. The hypothesized scenario for KAL gene evolution in primates is presented. Before the divergence of Platypus from mammals, the differentiation of sex chromosomes was initiated. After the divergence of prosimian from simian primates, stratum 4 was formed and the differentiation of KALX and KALY started. There were numerous, independent gene-conversion-like events (at least 10) during the evolution of primates, as indicated by the red stars. The arrows show the direction of conversion. The number in each red star corresponds to the conversion event identified in Figure 3.