You are studying aging in fruit flies and have generated a number of homozygous

Question

You are studying aging in fruit flies and have generated a number of homozygous long-lived mutants. You now wish to determine how many genes these six mutants represent. You perform pairwise crosses with all of the homozygous mutants to each other and to wild-type (WT) flies. Results of this analysis are shown in the table below ("+" indicates all offspring have normal lifespan; "–" indicates all offspring have longer mutant lifespan).

(a) Are these mutations dominant or recessive? Briefly describe how you reach your conclusion.

(b) Based on these results, how many genes are working here to affect lifespan? Indicate which mutations affect which gene(s).

Explanation / Answer

Part a- The mutation is recessive type because if dominant mutant cross with other fly the resultant progenies will always longer mutant lifespan. Here we are getting Wild type progenies also. Therefore, the mutation is recessive.

Part b- we can see that crosses between mutant 1, 3, and 4 results into mutant progenies. That means they have same gene mutation. Now cross between 6 and 2 is also have same gene mutation. Therefore, there are 3 genes are involving for the mutation. Only three genes 1,2 and 5 are responsible.

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