Heterozygous effects of x-ray induced mutations on viability of Drosophila melanogaster

Drosophila second chromosomes that had received 1000 R of X-irradiation mainly in the mature sperm stage were tested for heterozygous effects on viability. When the genetic background was heterozygous the viability was reduced by about 1.5 percent; in a nearly homozygous background the viability was enhanced by about the same amount. In a partially inbred background the results were intermediate. The results are therefore in agreement with earlier experiments of Wallace and Mukai.