Crossing over, or recombination, is thought to be evolutionarily advantageous because it continually shuffles genetic alleles into novel combinations. until recently, it was thought that y-linked genes might degenerate because they have no homologous genes on the x chromosome with which to recombine. however, when the y chromosome was sequenced, eight large regions were found to be internally homologous to each other, and quite a few of the 78 genes represent duplicates. how might this be beneficial?