You are trying to determine the mode of inheritance for the mutant curly-winged phenotype in Drosophila. You cross pure-bred wild-type flies with pure-bred mutant (curly-winged) flies and notice that all of F1 has curly wings. You make the scientific hypothesis that the curly-winged phenotype is autosomal dominant to the wild-type wing phenotype. a. If your scientific hypothesis is correct, what ratios would you expect to see in your F2 generation?

The correct answer is - In F2 generation we should get a 3:1 ratio of phenotypes. 3 curly dominant, 1 wild type recessive.

Explanation:

In the given case, the cross between pure-bred wild-type flies with pure-bred mutant (curly-winged) flies and it is found that in F1 generation all offsprings are curly wings which means curly wings are dominant over wild-type.

let assume w gene is responsible for wild type and W gene is responsible for the curly wings which is dominant over wild type

     W   W

w    Ww  Ww

w  Ww   Ww

now on self crossing

     W   w

W   Ww  Ww

w   Ww  ww

In f2 generation there are 75% chances of the curly wing and 25% chances of wild type or the ratio of phenotype would be 3:1

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