Question

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?

Answer 1

Step-by-step explanation:

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