Frozen Evolution. Or, that’s not the way it is, Mr. Darwin. A Farewell to Selfish Gene.

Another way in which an allele can spread through meoitic drive consists in programming the chromosome that carries the alternative allele to destroy or damage the gamete in which it will end up after the completion of meoisis. This mechanism occurs, e.g. in known systems in the fruit fly Drosophila melanogaster (segregation distortion, SD-systém) and in the house mouse Mus musculus (t-haplotype) (Carvalho & Vaz 1999; Ardlie 1998; Vanboven et al. 1996) (Fig. IV.11). In both cases, meiotic drive occurs during sperm formation and, in both cases, this leads to a smaller number of viable sperm in the ejaculate of a heterozygote male and, in both cases, most of the viable sperm contain the allele that causes this effect. Simultaneously, the destruction of the sex cells containing the normal allele is an active process from the standpoint of the normal allele. If the relevant chromosome does not contain the normal allele in the relevant locus because of deletion, the sperm is not destroyed. This means that the allele responsible for meiotic drive somehow manages to reprogram the normal allele so that, after completion of cell division, it actively damages the spermatid or sperm, in which the nucleus is located. However, it is a certain simplification to speak of an allele in this case; in actual fact, the relevant “allele” consists of a combination of several genes in closely adjacent loci.