Question

In the Japanese morning glory, purple flower color may be caused by dominant alleles at either one of two separate gene pairs, A_bb or aaB_. When dominant alleles are present at both gene pairs (A_B_), the flower color is blue, and when both are homozygous recessive (aabb), the color is scarlet. A blue F1 was therefore produced by crossing two different purple types AAbb x aaBB.

A. What phenotypes in what proportion would you expect from crossing this F1 to the AAbb parent?

B. What phenotypes in what proportion would you expect from crossing this F1 to the aaBB parent?

C. For an F1 x F1 cross, what proportion of the offspring would be expected to have purple flower color?

D. For an F1 x F1 cross, what proportion of the offspring would be expected to have blue flower color?

E. For an F1 x F1 cross, what proportion of the offspring would be expected to have scarlett flower color?

Answer 1

A.

F1 x AAbb

AaBb x AAbb

(AB, aB, Ab, ab) x Ab

AABb (Blue) : AaBb (Blue) : AAbb (Purple) : Aabb (Purple) = 1:1:1:1

Blue : Purple = 1:1

B.

F1 x aaBB

AaBb (F1) x aaBB

(AB, aB, Ab, ab) x aB

AaBB (blue) : aaBB (purple) : AaBb (blue) : aaBb (purple) = 1:1:1:1

Blue: Purple = 1:1

C.

F1 x F1

AaBb x AaBb

(AB, aB, Ab, ab) x (AB, aB, Ab, ab) - gametes

A_B_ (blue) = 9 - F2 genotypes

A_bb (purple) = 3

aaB_ (purple) = 3

aabb (scarlet) = 1

Blue: purple: scarlet = 9:6:1

9 out of 16 have purple flower color , 6 out of 16 have sacrley flower and 1 out of 16 have purple flower