Problem 6-8. Suppose that all individuals in a wild population of Drosophila mel

Question

Problem 6-8. Suppose that all individuals in a wild population of Drosophila melanogaster are homozygous for an inversion in chromosome 3 that spans 8 cM. Also suppose that all individuals in a second population are homozygous or hemizygous for an inversion in the X chromosome that spans 14 cM A female from the first population is mated with a male from the second to produce an Fl generation. Note that recombination (crossing over) does not occur in Drosophila males 6. As pertaining to the inversions, the female F1 progeny are best described as A. Balanced and heterozygous for inversions on chromosomes 3 and X B. Unbalanced and heterozygous for inversions on chromosomes 3 and X C. Balanced and heterozygous for the inversion on chromosome 3 only D. Unbalanced and heterozygous for the inversion on chromosome 3 only E. Balanced and heterozygous for the inversion on chromosome X only F. Unbalanced and heterozygous for the inversion on chromosome X only 7. Taking into account recombination (crossing over) and the size of the inversions, what proportion of the gametes from the F1 female should be unbalanced (for either inversion)? A. 0.08 C. 0.14 B. 0.92 D. 0.86 E. 0.79 F. 0.011 G. 0.069 H. 0.129 I. 0.209 J. 1.00 8. If the males and females generated by the cross (F1 generation) are allowed to randomly intermate, what portion of the next generation (F2) females should be heterozygous for both inversions? C. 1/4 B. 1/8D. 1/2 E. 2/3 F. 3/4 G. 14/16 H. 1

Explanation / Answer

6) When a female from the first population(inversion in autosome 3) is mated with a male from second population(inversion in X chromosome),the female F1 progeny will be described as balanced and heterozygous for inversions on chromosome 3 and X chromosome,because the females will contain normal X from first population and inversed X from second,and inversed Chromosome 3 from first population where normal chromosome 3 from second population.

7) F1 females gametes will give rise to four types of gametes if recombination is taken into account.Out of these four,three will contain inversions.So the proportion of unbalanced gametes is near 0.79

8) Males and females generated by F1 generation are allowed to mate randomly. Half(1/2)of the females heterozygous for X chromosome inversion as well as Chromosome 3

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