The Nature of Quantitative Genetic Variation in Drosophila. II* Average Dominance of Abdominal Bristle Polygenes

Abstract

A comparison of 13 abdominal bristle selection lines with their base population and with reciprocal Fls between the selection lines and the base population was carried out. There was no significant directional contribution of maternally inherited factors to selection response.Different estimates of average dominance ranged from 0·28 to 0·43 with a mean of 0·39. This indicates that the alleles increasing abdominal bristle number are, on average, partly recessive. Some of the possible consequences of this are discussed. IntroductionIn diploid organisms, the dominance of alleles affects their rate of change in frequency and probability of being lost during selection (Wright 1969). Consequently, the average dominance of alleles is one of the parameters that must be specified in describing the nature of genetic variation for quantitative characters.This series of studies is concerned with specifying the nature of genetic variation for abdominal bristle number in the Canberra population of Drosophila melanogaster. The objectives of this study were (1) to determine the average dominance of abdominal bristle polygenes by comparing selection lines and F 1 S between selection lines and their base population, and (2) to check for maternally inherited contributions to selection response.

Genetics of human obesity: lessons from mouse models and candidate genes

“…This distribution may in part fit with what have been identified from QTLmapping in experimental mouse crosses, where several loci have been identified, that explain between five and 20% of the phenotypical variation [54]. Studies of individual loci affecting bristle numbers in the fruit-fly has also revealed some more direct effects of epistasis when looking at selected lines [55,56].…”

Comparative losses of quantitative and molecular genetic variation in finite populations of Drosophila melanogaster

“…5N e )] 1/7 , and estimating the adjusted F values from equation (1). A proportion of the quantitative genetic variation for both abdominal and sternopleural bristle numbers is known to be due to sex-linked loci (Spickett & Thoday, 1966 ;Frankham, 1969Frankham, , 1977. As approximately 20 % of the Drosophila eukaryotic genome is X-linked, the inbreeding coefficients have been adjusted upwards based on this proportion, using the same procedure as above.…”

Divergent abdominal bristle patterns in two distantly related drosophilids: antero-posterior variations and sexual dimorphism in a modular trait

“…Surprisingly, in many cases nonhomologous segments were measured in female and male. For example, female A5 and male A4 (Frankham 1968a, b), or female A6 and male A5 , or the sum A5 + A6 in females and A4 + A5 in males (Frankham 1977).…”