Sequence of meiotic events in female Drosophila melanogaster Temperature‐sensitive periods of autosomal crossing‐over and secondary nondisjunction of X chromosomes

Abstract

In autosomal translocation/inversion bearing XXY females of Drosophila melanogaster the autosomal crossing‐over frequency is very sensitive to heat shock in an early meiotic stage which is coincidental with premeiotic DNA synthesis. The increase in autosomal crossing‐over caused an increase in X chromosome nondisjunction in the same oocytes. Following this stage a heat sensitive period more directly affecting nondisjunction occurs. At the end of this period there is a minor heat sensitive stage of crossing‐over. It is suggested that the sequence of meiotic events is as follows: 1) Determination of preconditions of crossing‐over, 2) non‐homologous and homologous chromosome pairing, 3) final determination of crossing‐over. © 1974 Mendelian Society of Lund