I expect to run into more discussions about mitochondrial DNA than none. Mitochondria are super important and we inherit them in an anomalous fashion. mtDNA comes exclusively from our mothers.
I had an itch last night to add some new factoids to my fleshy filing cabinet and started searching around. One of the first things that came up was this analysis of the 'Mother's Curse'. It's a fun theory and, apparently, a popular explanation for why women live longer.
The Mother’s Curse hypothesis posits that mothers curse their sons with harmful mitochondria, because maternal mitochondrial inheritance makes selection blind to mitochondrial mutations that harm only males. As a result, mitochondrial function may be evolutionarily optimized for females. This is an attractive explanation for ubiquitous sex differences in lifespan and aging, given the prevalence of maternal mitochondrial inheritance and the established relationship between mitochondria and aging.
The analysis points out all the expected dimensions of the curse (should it be true). But, generally, mtDNA as a cause for male unfortunateness is inconclusive. Chromosomal sex effects (male/female difference in nuclear DNA) are estimated to be greater than those of mtDNA, and without something like twin studies where only mtDNA differs, chromosomal effects are hard to distinguish from mtDNA effects.
My favorite expectation of the Mother's Curse are the more antagonistic aspects, ie females of a species unknowingly, yet purposefully, using mtDNA to harm males of the species. Sadly there's about as much evidence for this as there is for everything else:
While the evolution of sexual antagonism may be inevitable in species with separate sexes (Connallon and Clark, 2014), the evidence for sexually antagonistic mitochondrial mutations is somewhat limited. Such mutations have long been recognized in plants, where mitochondrial mutations in hermaphrodites have been found to increase female fertility while rendering males sterile, a phenomenon known as cytoplasmic male sterility (Lewis, 1941; Budar et al., 2003). In animals, recent studies have also found mitotypes with sexually antagonistic effects on both fertility and viability (Dowling and Adrian, 2019). As with the previous two patterns, negative intersexual correlations can also be caused by sex chromosome effects, rather than mitochondrial effects. Indeed, work on Drosophila has shown sexually antagonistic effects that are consistent with Mother’s Curse but difficult to disentangle from X chromosome effects (Rand et al., 2001). Given that X chromosomes are vastly larger than mitochondrial genomes, sex chromosome effects could be large.
@remindme in 252 days to thank my mother for her mitochondria.