In most cases in which the genetic basis of industrial melanism in moth has been analyzed, the melanic color pattern has been found to be due to a single dominant allele. in one study of a heavily polluted area observed a frequency of 87% melanic biston betularia. estimate the frequency of the dominant allele leading to melanism in this population and the expected frequencies of homozygous melanics, heterozygous melanics, and recessive homozygotes.