Genes that generate phenotypes beneficial to one sex but deleterious to the other. For example, a gene that produces a colorful pattern on the sides of a fish might be useful for males that participate in mating displays to attract females. It would be deleterious to females if it made them more vunerable to predation. The accumulation of such genes on the Y chromosome would ensure that they are expressed only in males, provided mechanisms evolve that prevent recombination between the X and Y chromosomes in males.
Subjects: Genetics and Genomics.