Localizing genes that defer senescence in Drosophila melanogaster.

Selection for age-specific reproduction has produced replicate stocks in which life span exceeds that in short-lived controls by about 30 per cent, in unpaired individuals. Crosses between a selected long-lived (L) stock, short-lived (S) stock and a strain with balancer chromosomes were used to create all possible combinations of their chromosomes. The longest and shortest-lived genotypes are found to be (LSL) and (SLS), with other combinations distributed between them approximately according to their first and third chromosomes. Longevity appears to be under polygenic control with contributing elements on all chromosomes. The third chromosome is by far the most influential, accounting for 66 to 72 per cent of the observed variation in females. The first chromosome is less effective. Epistatic interactions are more important in males than females, but are significant only in measurements of single individuals. Some controlling elements for longevity appear to differ in males and females. Crosses of selected stocks with known P and M-cytotype strains show no effect on either sterility or longevity.