POLYGENIC SEGREGATION WITHIN AN ISOFEMALE STRAIN OF DROSOPHILA

Abstract

Isofemale strains provide a sample of the genetic variation in a natural population. Phenotypically distinct chromosomes have been identified segregating within an isofemale strain of Drosophila melanogaster by extracting and progeny testing samples of single whole second and third chromosomes influencing sternopleural bristle number. Given ample opportunity for recombination to occur among linked polygenic complexes, the ability to detect clear segregation suggests that the polygenic makeup of the sampled trait may not involve large numbers of genes. Using such a sampling approach, it should be possible to quantify chromosome-level polymorphisms affecting quantitative expression. This possibility was tested using computer simulations of the progeny testing component to assess the sensitivity of the breeding program used in polygenic analysis. These computer simulations help define the optimum design for progeny testing experiments.