Cytoplasmic suppressor effect on male crossing over in Drosophila ananassae.

Abstract

A reciprocal cross difference in the frequency of male recombination was detected in progeny of hybrids between e se; bri vu and Tonga stocks of Drosophila ananassae.A chromosomal enhancer-cytoplasmic suppressor system determining male crossing over in D. ananassae was identified that appeared to be similar to, but distinct from, that described previously by Hinton (1974). The higher the temperature at which males were reared, the less reciprocal cross ratio in the frequency of male recombination was found. The reciprocal cross differences might be explained by a cytoplasmic suppressor of the Tonga stock and a nuclear chromosomal gene(s).This chromosomal gene is dominant for the reducing the frequency of male recombination, and is located on the 2nd chromosome of the Tonga stock.The maternally transmitted cytoplasmic suppressor was maintained by other chromosomal regions (genes) on both 2nd and 3rd chromosomes of the Tonga stock.

A site specific increase in recombination in Drosophila ananassae.

“…Based on the results of an allelism test, the first two enhancers seem to be allelic, but En(2)-hn appears to be a pseudoallele or a closely linked separate locus (Matsuda andTobari, 1983, 1987). In the present experiment, we found a new enhancer, designated as En(2)-ep, and mapped it at 0.1 map unit to the right of the Om(2C) locus.…”

“…The L8 wild type stock is the same as that previously used by . The e 65 pi; bri ru (8N-2) stock is an inbred sub-line of the e 65 pi; bri ru stock (Goñi, 1989), which is a derivative of the e 65 Arc pi; bri ru stock used in the previous experiments (Matsuda andTobari, 1983, 1987 same as that used by Hinton (1970). The genetic symbols follow the description by Tobari (1975, 1993).…”

“…The genetic system that controls crossing over in males of D. ananassae is a complex one and is composed of several enhancers and a suppressor mapped on chromosome 2 and 3 (Hinton, 1970;Matsuda et al, 1993). In addition, two different extrachromosomal suppressors of crossing over in males have been reported by Hinton (1974) and Matsuda (1989). observed that chiasmata exist in males at a frequency which can account for the increased rate of recombination in males thus suggesting the meiotic origin.…”