An estimate of heterosis inDrosophila melanogaster

Abstract

SUMMARYTwenty-five population cages ofD. melanogasterwere set up, each containing a different wild-type second chromosome and the marker chromosomeCy. In all but one case where contamination apparently occurred, theCychromosome persisted in the population at high frequency, showing a selective advantage ofCy/ + heterozygotes over wild-type homozygotes. Overall, the results indicate that homozygosity of the entire second chromosome causes a depression in fitness of the order of 85%.