Transpositions of the bobbed locus in Drosophila melanogaster

摘要

Due to the complete absence of ribosomal DNA the Xbb~-chromosome of Drosophila is lethal both in homozygous conditions and in compound with the Xbb~- chromosome. However, in the cross between the C(1)RM/Ybb~- females and the Xbb~-/B~sYbb~+ males, characterized by the development of lethal Xbb~-/Ybb~- zygotes, two fertile males were detected. These males possessed all the markers of the Xbb~- chromosome but lacked the Y chromosome B~s marker, Genetic analysis of their progeny showed that genes responsible for restoration of viability and fertility of these exceptional male were associated with the X chromosome. The crossover tests showed that in one case these genes were tightly linked to the w locus, and in the second case they were located 12.6 map units to the right of the Tu locus. It has also been shown that the bb locus was transposed to the X chromosome within the short arm of Y chromosome. Transposition of the B~sYbb~+ chromosome-specific rDNA sequences to the X chromosome was confirmed by means of Southern blotting. These data indicate that replacement of the bb locus is realized by transposition rather than recombination.