The Distribution of X-Ray Induced Crossovers from Curly Inversion Heterozygotes of Drosophila melanogaster Females

Abstract

That crossing may occur in oogonial cells was suggested by the results of experiments by Whittinghill [1] in which crossing over was induced by x-rays in the X-chromosomes of Drosophila females homozygous for the c3G asynaptic factor. It had previously been demonstrated that induced crossovers recovered from Drosophila males were of spermatogonial origin [2,3]. Cooper's observations [4] of chiasmata in gonial cells of both sexes of Drosophila may provide cytological foundations for the hypothesis of gonial origin of some crossovers, particularly those which are x-ray induced. Somatic crossing over, the basis for the occurranece of twin spots in the hypodermis of Drosophilamales and females [5], closely parallels gonial crossing over in the formation of daughter cells which have become homozygous distally. The possible consequences of oogonial crossing over upon linking data, as recently discussed by Whittinghill [6], illustrate the need for further investigation of this phenomena. This paper reports the results of x-ray induced crossing over in Curly inversion heterozygotes of Drosophila melanogaster females, and these results are interpreted in relation to normal, or random, meiotic events as opposed to oogonial events of recombination.

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