Question

A Haploid yeast strain that is deficient in its ability to make arginine, is crossed to a different haploid yeast strain also unable to produce arginine. The resulting diploid, F1 strain is able to make its own arginine. What is the best explanation?

1. Each deficient haploid strain possessed a mutant allele, but not in the same gene, thus the diploid had 1 functional copy of each gene
2. The defective arginine biosynthetic enzymes, made from the mutant genes, were able to interact and make arginine
3. A crossing over event with one of the yeast strains gave a functional allele of the arginine biosynthesis gene

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The genes A, B, and C are tightly linked to each other on the same chromosome. The genes are 2 map units away from each other. A-B=2 map units, B-C=2 map units, and A-C= 4 map units.

You cross an organism that AABBCC to one that is aabbcc. You take the F1 heterozygote and cross it to aabbcc. How many offspring should you screen to observe the rare event (a double crossover progeny?)

1 – (probability of not getting rare event)ⁿ = 0.95

1. 73
2. 7489
3. 36
4. 148
5. 14978

Answer 1

each haploid strains are not able to make arginine but the F1 can produce arginine this shows mutations in the deficient strains are on different genes so that the F1 progeny has a functional copy of each gene so that the pathway of synthesizing arginine is completed   so the answer is A) Each deficient haploid strain possessed a mutant allele, but not in the same gene, thus the diploid had 1 functional copy of each gene