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A new type of position effect called the "trans-vection effect" permits rapid and highly efficient detection of chromosomal rearrangements in the first generation following an induction treatment. Several unique features are involved: (1) the position effect extends over vastly greater distances than heretofore demonstrated (over 500 discs of the salivary gland chromosomes); (2) wholly euchromatic as well as euchromatic-heterochromatic rearrangements are efficiently detected; and (3) the position effect is detectable only in a double heterozygote between pseudoallelic mutant genes, the arrangement of which must be of the trans-type (a +/+ b). Interference in somatic pairing exerted by structural heterozygosity is postulated to reduce the transport of an essential gene product from one chromosome of this heterozygote to the other. By the use of this new method fast (pile) neutrons have been found to be more effective than X-rays or gamma rays in producing rearrangements in Drosophila, and estimates of the dose of fast neutrons at different stations during a nuclear detonation have been derived.
E. B. Lewis (Thu,) studied this question.