On the Viability Effects of Chromosomes in Drosophila

Abstract

Rank-order selection seriously alters some of the questions commonly asked by population geneticists. The average degree of dominance of detrimental mutations, for example, is not as relevant to events transpiring within populations of diploid organisms as is the nature of those chromosomes (or alleles) carried by zygotes that actually survive and reproduce. Changing the question requires changing the experimental analyses as well. Rather than ask, What is the average viability of heterozygotes that carry chromosomes of a given sort? one should ask, What sorts of chromosomes are carried by heterozygotes of a given viability? The greatest interest, of course, lies with those heterozygotes that, of all zygotes, are the ones most likely to survive and reproduce. The chief purposes of the present article are (1) to present summary data (table 1) listing the average viability of homozygotes carried by heterozygotes of different viabilities as determined by a reanalysis of data collected during the 1950s on irr...