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ANALYSIS OF PRODUCTS FROM REGULARLY OCCURRING ASYMMETRICAL EXCHANGE IN DROSOPHILA MELANOGASTER

1961; Oxford University Press; Volume: 46; Issue: 12 Linguagem: Inglês

10.1093/genetics/46.12.1687

1943-2631

B H Judd,

Insect Resistance and Genetics

regular occurrence of a deficiency product, apparently resulting from TEssing over within an asymmetrically-paired segment of the Drosophila melanogaster X chromosome was reported by GREEN (1959). JUDD (1961) recovered the complementary duplication and deficiency strands from an asymmetrical exchange occurring within the white locus. Although the recombinant products analyzed by these two investigators are quite different, they are related since both demonstrate recombination in chromosome segments which are not specifically paired in a point-by-point manner. Prior to these investigations, asymmetrical crossover products were, in general, expected only from chromosomes bearing tandem duplications. The regular recovery of duplication and deficiency recombinant products from structurally normal chromosomes allows several questions bearing on the mechanism of crossing over to be raised. First, since the exceptional types appear among the offspring from several different crosses, it is of interest to determine whether the non-homologous pairing is accomplished in precisely the same manner in each case, with subsequent crossing over always occurring at the same point. This would lead to a single type of duplication and the complementary deficiency. On the other hand, if pairing may occur in any one of several ways or if crossing over may take place at one of several places within the noa-homologously paired region, duplication and deficiency products of several different types should be obtained. A related question is whether the asymmetrical pairing involves truly non-homologous chromosome regions or whether seemingly unrelated parts have retained some specific synaptic affinities during their evolution. In other words, how specific must pairing be in order to allow crossing over? Also, since the exceptional products are recovered from some crosses but not from others, a question is raised as to what genetic elements might be involved in determining this process. Unlike the results reported by GREEN (1959) , three different deficiency products and one duplication type have thus far been recovered from various crosses during the course of a study involving the spatial relationships between some white homoalleles and heteroalleles. A detailed genetic and cytological analysis 1This investigation was supported by PHS grant RG-6492 from the National Institutes of