Figure 8.

Model for the Distribution of the Two Haplotypes.

The original zygospore that all standard laboratory strains are derived from is hypothesized to be the product of a mating between two strains that were 2% divergent in sequence, depicted here as blue versus yellow. In subsequent crosses, the resulting progeny lost much of this genetic variation so that in extant strains today there is only one haplotype for 74.8% of the genome. The other 25.2% of the genome may have one of two possible haplotypes in each strain, depending on which ancestral parent donated a given locus to that strain. Here, we arbitrarily designated the haplotype of the reference strain as haplotype 1 and the alternate as haplotype 2. Haplotype 2 regions are recognized by the relatively high (2%) frequency of variants relative to the reference strain.