A test of the influence of isoallelic variation upon a quantitative character.

In order to test the assumption that isoalleles can contribute to polygenic variation, several isoalleles of cubitus interruptus were examined for their influence upon the quantitative expression of a related venation mutant, veinlet. In spite of the fact that veinlet and cubitus interruptus affect closely related developmental processes, the ci isoalleles had no effect upon the expression of veinlet. This test does not, of course, disprove the hypothesis that isoalleles play a part in polygenic variation. It is clear, however, that not all seemingly relevant isoalleles are necessarily effective elements in a given polygenic system.