Drosophila female, diheterozygous for genes C and D, is crossed with a recessive male. In the offspring, cleavage was obtained in the ratio: 43.5% CcDd; 6.5% Ccdd; 6.5% ccDd; 43.5% ccdd. Determine: 1) the C and D genes are in the cis or trans position; 2) the distance between genes C and D in morganids.
There are more non-crossover gametes of the female, which means that genes C and D are on one chromosome, and genes c and d are on the other chromosome of the same pair, that is, the genes are in the cis position. 6.5% + 6.5% = 13%, or 13 morganids.
Answer: 1) genes C and D are in the cis position; 2) the distance between genes C and D is 13 morganids.
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