Why did Fair Meiosis evolve?

Question

How and why did Fair Meiosis evolve? I can hardly think that it provided a fitness advantage to the individual carrying the mutation. Why would it? Or did it evolve through lineage selection? Or was it some kind of pre-existing characteristic of meiosis that have no energy cost and therefore never disappear?UPDATE:I call fair meiosis the process of meiosis in which each chromosome has an equal chance of transmission.I'm trying to make my questions clearer.Is there any selection pressure in favour of alleles causing a fair meiosis? If yes, why? It doesn't seem to me to provide any advantage to the individual carrying this allele.

Answer 1

You asked this question more than five months ago, but you or someone else might still find an answer helpful.

It might help to consider your question from the reverse perspective: what are the consequences of unfair meiosis?

We know that there are selfish genetic elements throughout the genome. Some of these are segregation distorters which cause the chromosome they are on to be represented in more than half the gametes. A particularly well-studied segregation distorter is the SD complex in fruit flies. In males, this set of linked genes kills sperm not carrying the complex. As a result, in heterozygotes (which carry the SD complex on one chromosome) most living sperm carry the chromosome with the SD complex. This is a classic example of unfair meiosis.

Unfair segregation is beneficial for the SD complex as it will be present in most offspring instead of only 50% of offspring. For the organism as a whole, however, this reduces fitness. Heterozygote males will produce fewer sperm, and thus be less successful in sperm competition with other males. So males with the SD complex will produce fewer offspring, which is bad for them and bad for all genes in the genome other than the SD complex. This results in selection on other genes in the genome to suppress the segregation distorter.

Similarly, assume a mechanism evolved that resulted in the transmission of only maternal chromosomes. Selection will favor genes on paternal chromosomes that suppress any segregation biasing genes on the maternal chromosomes since not doing so will reduce the fitness of paternal genes.

So the short answer is that someone (the organism, other genes) incurs a cost from biased segregation, so selection favors mechanisms to suppress the genes that cause the bias.