Fertility Costs of Meiotic Drivers

Abstract

In sexual reproduction, opportunities are limited and the stakes are high. This inevitably leads to conflict. One pervasive conflict occurs within genomes between alternative alleles at heterozygous loci. Each gamete and thus each offspring will inherit only one of the two alleles from a heterozygous parent. Most alleles 'play fair' and have a 50% chance of being included in any given gamete. However, alleles can gain an enormous advantage if they act selfishly to force their own transmission into more than half, sometimes even all, of the functional gametes. These selfish alleles are known as 'meiotic drivers', and their cheating often incurs a high cost on the fertility of eukaryotes ranging from plants to mammals. Here, we review how several types of meiotic drivers directly and indirectly contribute to infertility, and argue that a complete picture of the genetics of infertility will require focusing on both the standard alleles - those that play fair - as well as selfish alleles involved in genetic conflict.

Figure 1:

Tree representing the genera containing drivers cited in this work. This is only a subset of the organisms in which drive has been observed.

Figure 2:

Models representing general mechanisms of meiotic drive. The box on the left depicts two types of ‘true’ meiotic drive. The example on left shows biased transmission favoring the ‘a’ allele during meiosis I and/or meiosis II. In the example on the right, the ‘a’ allele gains a transmission advantage by disrupting meiosis II of the chromosome that inherits ‘A.’ The box on the right depicts gamete killing meiotic drive where the developing gametes that inherit the ‘a’ allele destroy those that inherit ‘A.’

Figure 3:

A schematic depicting how meiotic drivers can directly and indirectly contribute to infertility.