7. The map of a chromosome interval is: A10 mu40 muC low many double crossovers

Question

7. The map of a chromosome interval is: A10 mu40 muC low many double crossovers would be expected out of 1000 progeny from the cross: Abe l aBC x abc I abc 8. In Drosophila, the genes y (yellow body) and car (carnation eyes) are located at opposite ends of the X chromosome. In doubly heterozygous females ( car* /y car), a single chiasma is observed somewhere along the X chromosome in 90% of the examined oocytes. No X chromosomes with multiple chiasmata are observed. What percentage of the male progeny from such a female would be recombinant for y and car?

Explanation / Answer

Ans 7.  Expected double crossovers (ie between A & C)= 10*40/1000=0.4*100=40 double cross

Ans 8. 45%

In Drosophila, the genes y (yellow body) and car (carnation eyes) are located at opposite ends of the X chromosome. In doubly heterozygous females (y+ car+/y car), a single chiasma is observed somewhere along the X chromosome in 90% of the examined oocytes. No X chromosomes with multiple chiasmata are observed. show 1:1 ratio of progeny after crossingover so 50% of total a single chiasma is observed somewhere along the X chromosome in 90% of the examined oocytes.

so, 90*50100=45%

percentage of the male progeny from such a female would be recombinant for y and car.

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