A test cross was made between true-breeding EEWW flies and eeww flies. The resulting F1 generation was then crossed with eeww flies. 100 offspring in the F2 generation were examined, and it was discovered that the E and W genes were not linked. Which is the correct genotype of the F2 offspring if the genes were linked and if the genes were not linked?

Question

Biology

Aliza Estes

10 October, 01:41

A test cross was made between true-breeding EEWW flies and eeww flies. The resulting F1 generation was then crossed with eeww flies. 100 offspring in the F2 generation were examined, and it was discovered that the E and W genes were not linked. Which is the correct genotype of the F2 offspring if the genes were linked and if the genes were not linked?

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Nico Wilkerson · Answer 1

If the genes were linked:

Parental cross: EW/EW X ew/ew

F1 genotype: EW/ew

F1 Gametes:

- Parentals (more abundant) : EW and ew

- Recombinant (less abundant) : Ew and eW

Test cross: EW/ew X ew/ew

F2 genotypes:

Parentals: EW/ew; ew/ew; Recombinant: Ew/ew; eW/ew

If the genes are not linked:

Parental cross: EEWW X eeww

F1 genotype: EeWw

F1 gametes: EW, Ew, eW, ew. Genes assort independently, so all of the possible gametes of the F1 individual will have the same probability.

Test cross: EeWw X eeww

F2 genotypes:

1/4 EeWw, 1/4 Eeww, 1/4 eeWw, 1/4 eeww