Impact of Migration and Fitness on the Stability of Lethal t-Haplotype Polymorphism in Mus musculus: A Computer Study

[摘要] The t -haplotype is a chromosomal region in Mus musculus characterized by meiotic drive such that heterozygous males transmit t -bearing chromosomes to roughly 90% of their offspring. Most naturally occurring t -haplotypes express a recessive embryonic lethality, preventing fixation of the t -haplotype. Surprisingly, the t -haplotype occurs in nature as a persistent, low-frequency polymorphism. Early modeling studies led Lewontin to hypothesize that this low level polymorphism results from a balance between genetic drift in small demes and interdemic migration. Here, we show that while combinations of deme size and migration rate that predict natural t -haplotype frequencies exist, the range of such values is too narrow to be biologically plausible, suggesting that small deme size and interdemic migration alone do not explain the observed t -haplotype frequencies. In response, we tested other factors that might explain the observed t -polymorphism. Two led to biologically plausible models: substantially reduced heterozygous fitness and reduced meiotic drive. This raises the question whether these phenomena occur in nature. Our data suggest an alternative explanation: there is no stable, low-level t -polymorphism. Rather wild populations are in one of two stable states characterized by extinction of the t -haplotype and a high t -haplotype frequency, respectively, or in transition between the two.

[学科分类] 医学（综合）