Studies of rearrangements involving heterochromatin in Drosophila melanogaster. I. A proof of variegated-type position effect at the white locus. II. A study of the heterochromatin of chromosome IV

Abstract

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The X-IV translocation, [...], is shown to contain the wild-type allele, [...], at the white locus. This [...] has been replaced with a mutant gene, w, and a comparison of R([...])/w with R(w)/w[...] shows the former to give a variegated white phenotype while the latter is completely wild-type. It is concluded that the white variegation is due to an instability in the action of [...] when it is located in the rearranged chromosome.

Cold temperature enhances variegation particularly when applied during the embryonic stages of development. A less sensitive period is found to exist during the pupal stages. These facts indicate the white gene is active during more than a single period of development.

Twelve duplication-deficiency types have been obtained by combining the left and right parts of four X-IV translocations. Tests for survival of these combinations in the haplo-IV condition give somewhat contradictory results. These results are discussed and a possible order for the fourth chromosome translocation breaks is given.

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