An Effect of Temperature and Age on Crossing-Over in the First Chromosome of Drosophila Melanogaster

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Abstract
The discovery of bobbed (locus 70.0) at the extreme right end of the X-chromosome makes it possible for the first time to study the effect of external conditions on recombination values in this region and to test whether there is a causal connection between susceptibility to crossing-over and spindle-fiber attachment. Recombination values for the Bar-bobbed loci at 25 and 30[degree]C, and for 2-day periods were determined. The results show that 9 raised at 30[degree]C. gave a markedly higher recombination percentage during the first 3 or 4 periods of transfer. Both 25 and 30[degree]C. [female] show a 1st minimum value at the 4th or 5th day of the [female] ''s life. The difference in recombination percentage between 25 and 30[degree]C. disappeared at about the 9th day. The results indicate a causal connection between spindle-fiber attachment and susceptibility of the process of crossing over to external conditions.