Further studies on the interchromosomal effect on crossing over in Drosophila melanogaster affecting the preconditions of exchange.

The second chromosome inversion In (2L+2R) Cy in a heterozygous condition was studied for its effect on frequency and interference of crossing over in three different regions of the X chromosome of Drosophila melanogaster. A significant increase in crossing over frequency was observed in the proximal and distal regions of the X chromosome while in the middle of the chromosome crossing over frequency remained unaltered. The effect on interference remained unaltered at both ends of the X chromosome while a significant decrease was observed in the middle of the chromosome. These results suggest that the interchromosomal effect on crossing over affects the preconditions of exchange differently in different regions of the X chromosome, and possibly the duration of chromosome pairing.