Genetic load in a repeatedly irradiated Drosophila melanogaster population

A population of Drosophila melanogaster irradiated at an early larval stage in the course of more than one hundred generations with 1120 R, and its non-irradiated control population with the same isogenic background, were investigated. The frequency of the second chromosome recessive lethals as well as with their allelism and the viability of individual chromosomes when homozygous and heterozygous were analysed. In some respects considerable differences were established between the two populations. The irradiated population had a higher frequency of lethals and a different distribution of viability of homozygous, lethal-free chromosomes than the control. However, the frequency of allelism among the lethals was higher in the control population. No effects of dominance of the recessive lethals were detected in the material studied.