Bookmark On the Isle of Man off the coast of Ireland, a curious cat referred to as a manx cat was described in 1845. It had long hind legs and a short tail. Further work showed that the manx characteristics were the result of a dominant M allele at a single locus. An MM zygote would not survive, but Mm genotypes produced the manx characteristics. Imagine a scenario where the M allele arises by mutation on the Isle of Man. Explain how genetic drift could cause the M allele to reach a relatively high frequency (freq(M) > 0.25), even though it has harmful effects on fitness. Solution When the M allele is dominant and also deleterious when it is in the homozygous state. In the heterozygote stage Mm, the deleterious M allele is hidden due to which the selection will not eliminate it. The Mm genotypes are successful, so the frequency of M allele rises in the population. So the genetic drift selection cannot eliminate the M allele completely..