The distributive effect of selenoaminoacid treatment on crossing-over in Drosophila melanogaster.

the relative densities of double-exchange in the three segment intermediate and a reverse shift to the 1.63 p . ~ values at 81.6 p . Analysis of these shifts indicated that relative initial attenuation of coincident crossovers was always least in y-cv; results were equivocal with regard to the relative attenuation in CULU and U-f. These results are interpreted according to the polaron-hybrid DNA model of WHITEHOUSE as supporting the hypothesis that chromosomal protein, linearly associated with the DNA, mechan-ically induces breakage in the latter. The treatment curves for single-exchange chromosomes show considerable evidence of treatment effects on single segments, with little effect on the frequency for the total segment. These effects, which do not show obvious correlation to patterns for coincident crossovers in the corresponding segments, and effects in the control to 1.63 JAM range, have not been elucidated.