Studies on male recombination in a Southern Greek Drosophila melanogaster population

Abstract

SUMMARY: A combined cytological and genetic analysis has been carried out to determine whether the spontaneous male recombination associated with a line of Drosophila melanogaster derived from Southern Greece (31.1 MRF) involves chromosome breakage and random reunion. In all crosses showing male recombination, extensive abnormalities involving anaphase bridges and fragments were found at first and second meiotic divisions. This confirms that the low level of recombination associated with male recombination lines is not produced by normal, controlled crossing-over of the type found in females, but by chance reunions, following more erratic breakage events at first and second anaphase. In addition the occurrence of some limited premeiotic recombination cannot be excluded. The 31.1 MRF system shows higher recombination levels at elevated temperatures (29 °C) and chromosome abnormality frequency is also greatly increased. The 31.1 MRF induces both male recombination and chromosomal abnormalities at meiosis when it is inherited from females deriving their cytoplasm from stock other than CyL⁴/Pm. It is concluded that this factor acts independently of sex and that the reciprocal cross effect is caused by a cytoplasmic factor which the 31.1/CyL⁴ strain inherited from the CyL⁴/Pm stock.