Inbreeding and Genetic Loads in Irradiated Experimental Populations of Drosophila melanogaster

Abstract

Morton, Crow and Muller¹ suggested that measurements of the inbreeding depression can be used to estimate the magnitude of the genetic loads which populations carry as well as to differentiate between the mutational and balanced components of such loads. Several studies designed to investigate this problem have been done in Drosophila^2–6 and in Tribolium⁷. The validity of the technique proposed by Morton, Crow and Muller has been questioned (see Levene⁸ and Dobzhansky⁹ for references). Inbreeding investigations, nevertheless, remain useful to the examination of genetic loads in populations, although the possibilities of discrimination between the mutational and balanced components have become remote. This communication summarizes the results obtained from investigations aimed at comparing the magnitudes of the genetic loads in experimental populations of Drosophila melanogaster. These populations have been exposed to X-irradiation (to the males) for a number of generations and then maintained without further irradiation for varying periods of time. Their radiation histories are outlined in Table 1.