Sex is for sisters: intragenomic recombination and homology-dependent mutation as sources of evolutionary variation.

Sex and recombination generate variation via processes that depend on an underlying complementarity between participants. Sex between DNA segments depends on their sequences having enough in common. Viewed in this way, sex does not depend on genes that originate in separate cells. Sex in the single genome uses many of the same mechanisms as intergenomic sex but has not been properly appreciated as a source of variation or as a selectable process. Mutation is the generation of new sequences rather than the novel grouping of pre-existing alleles. Mechanisms of mutation that depend on pre-existing sequence similarities in the haploid genome are a source of variation with significant and special characteristics.