The synthesis of a purple pigment in petunia flowers is controlled by two genes,

Question

The synthesis of a purple pigment in petunia flowers is controlled by two genes, A and B, that are located on separate chromosomes. The biosynthetic pathway for pigment synthesis is: Mutations in gene A and gene B are recessive.

white -----gene A/ enzyme---> red intermidate ----- gene B / enzyme ----> purple pigment

a. What color flowers would you expect in a pure-breeding petunia null mutants unable to catalyze the first reaction? (2 points)

b. What color flowers would you expect in a pure-breeding petunia mutants unable to catalyze the second reaction? (2 points)

c. When the plants in parts a and b are crossed, what color flowers will the F1 petunia plants have? Explain your reasoning for your answer. (3 points)

d. What ratio of purple : red : white flowered plants would you expect in the F2? (4 points)

Explanation / Answer

Answer :

A) colors of the flower would be white.

b) the flowers would be red in color

c) petunia flowers will have purple color in F1 generation.

d) ratio between purple: red: white = 2:1:1

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