Mechanisms contributing to non-recovery of translocations induced in meiotic cells.

A cytological analysis of 22 and 7 autosomal (2;3) translocations induced, respectively, in mature and immature oocytes of Drosophila melanogaster appeared to be random in the distribution of the breaks. This finding is contrary to that expected if, as suggested by the mechanism of directed disjunction, the chromosomes involved in interchange at the centric region tended to be distributed to opposite poles at division I of meiosis. In each arm, the breaks were distributed more or less at random between the centromere and the telomere. However, in the translocations from the immature oocytes, the break-telomere distances of the segments interchanged showed a positive correlation, indicating that translocations induced in meiotic prophase and having a highly disproportionate length of segments interchanged are prone to be eliminated at division II by non-random disjunction of heteromorphic dyads.