In some plants, true-breeding, ref-flowed strains give all pink flowers when cro

ID: 86880 • Letter: I

Question

In some plants, true-breeding, ref-flowed strains give all pink flowers when crossed with a white flowered strain. Recall that axial flowers are dominant to terminal flowers.

a) What would be the expected genotypics and phenotypic proportions of the offspring resulting from a cross between a true-breeding axial, red plant and a terminal, white plant.

b) if the offspring in the above cross were mated (F1 generation mated), what would be the expected phenotypic proportions of their offspring (The F2 generation).

Explanation / Answer

a)The genotypes of the parents are AARR and aarr. Therefore the gametes of the parents must be AR and ar so the genotype for all the offspring in the F1 generation will be AaRr, and their phenotype will be axial-pink.

b)The ratio of genotypes can be determined by examining the Punnett square below:

AR Ar aR ar

AR AARR AARr AaRR AaRr

Ar AARr AArr AaRr Aarr

aR AaRR AaRr aaRR aaRr

ar AaRr Aarr aaRr aarr

The ratio of phenotypes will be:

6 axial-pink

8 pink

3 axial-red

4 red

3 axial-white

4 white

2 terminal-pink

12 axial

1 terminal-white

4 terminal

1 terminal-red