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Selection for and against a canalized phenotype in Drosophila melanogaster

Published online by Cambridge University Press:  14 April 2009

S. S. Y. Young
S. S. Y. Young
Affiliation:
C.S.I.R.O., Division of Animal Genetics, Delhi Road, North Ryde, N.S.W., Australia

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Selection for and against the canalized phenotype in scutellar bristles was attempted in two selection lines and a randomly selected line was used as control. The selection lines were the Decanalization line (D) and the Canalization line (N). The D line was maintained by matings of scute males (scwbl) with three scutellars with wild-type females (scwbl/yw) with five bristles, in the N line scute males with four bristles were mated with wild-type females also with four bristles, while in the C line males and females of the above genotypes were selected at random. The lines were established from a sample of flies taken from a line selected for high scutellar numbers.

After eighteen generations of selection the C line was characterized by a regression of mean bristle number without appreciable change in variance. Relative to the N line, the D population showed a lower proportion of flies having four scutellars, a higher variance in bristle numbers, and a higher proportion of four-bristle scute flies having abnormal patterns.

Two alternative hypotheses were advanced to account for the results of this experiment. The first postulated a relative change in the widths of the four-bristle canalization zones in the selection lines, while the second suggested a relative change in frequencies of specific modifier genes for scutellars in scute and in wild-type genotypes of the lines. The evidence favours the latter hypothesis.

Type
Research Article
Information
Genetics Research , Volume 10 , Issue 1 , August 1967 , pp. 21 - 33
Copyright
Copyright © Cambridge University Press 1967

References

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