Fig. 1.

Three possible consequences of maternal transmission of mitochondria (and other maternally transmitted organelles and symbionts). (A) Mutations that are deleterious in males can become common if they do not decrease female fitness. (B) Maternally transmitted lineages that increase the frequency of females will be favored by selection. (C) Mitochondria and maternally transmitted symbionts are linked, such that symbionts that spread in a population will bring their associated mitochondrial haplotype along with them. Different colors represent different haplotypes. Mt, mitochondria; S, symbiont.