Potential variance affecting homeotic Ultrabithorax and Antennapedia phenotypes in Drosophila melanogaster.
Introgression of homeotic mutations into wild-type genetic backgrounds results in a wide variety of phenotypes and implies that major effect modifiers of extreme phenotypes are not uncommon in natural populations of Drosophila. A composite interval mapping procedure was used to demonstrate that one major effect locus accounts for three-quarters of the variance for haltere to wing margin transformation in Ultrabithorax flies, yet has no obvious effect on wild-type development. Several other genetic backgrounds result in enlargement of the haltere significantly beyond the normal range of haploinsufficient phenotypes, suggesting genetic variation in cofactors that mediate homeotic protein function. Introgression of Antennapedia produces lines with heritable phenotypes ranging from almost complete suppression to perfect antennal leg formation, as well as transformations that are restricted to either the distal or proximal portion of the appendage. It is argued that the existence of "potential" variance, which is genetic variation whose effects are not observable in wild-type individuals, is a prerequisite for the uncoupling of genetic from phenotypic divergence.
Gibson
G
G
Department of Biology, University of Michigan, Ann Arbor, Michigan 48109, USA.ggibson@unity.ncsu.edu
Wemple
M
M
van Helden
S
S
D000704:Analysis of Variance; D000818:Animals; D051943:Antennapedia Homeodomain Protein; D003433:Crosses, Genetic; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005801:Genes, Homeobox / Q000502:physiology*; D014644:Genetic Variation; D005838:Genotype; D018398:Homeodomain Proteins / Q000235:genetics*; D019476:Insect Proteins; D008297:Male; D018895:Microsatellite Repeats; D009687:Nuclear Proteins; D010641:Phenotype; D014157:Transcription Factors
D051943:Antennapedia Homeodomain Protein; C497974:Antp protein, Drosophila; D017931:DNA Primers; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila