In pea plants, two separate, recessive mutations result in white flowers. Crossi
ID: 35205 • Letter: I
Question
In pea plants, two separate, recessive mutations result in white flowers. Crossing plants true-breeding for the gene A mutation with plants true-breeding for the gene B mutation unexpectedly results in an F1 with purple flowers. A plant geneticist has worked out the metabolic pathway that results in the purple coloration, shown below.
If the F1 is self-fertilized, what ratio of purple:white plants would you expect in the F2?
Question options:
13:3
15:1
1:15
3:13
9:7
7:9
13:3
15:1
1:15
3:13
9:7
7:9
Explanation / Answer
When F1 is self-fertilized,
purple( AaBb) * purple( AaBb)
AB
Ab
aB
ab
AB
AABB
AABb
AaBB
AaBb
Ab
AABb
AAbb
AaBb
Aabb
aB
AaBB
AaBb
aaBB
aaBb
ab
AaBb
Aabb
aaBb
aabb
A_B_ : give purple color as both the genes are functional.
A_bb : give colorless product as A is functional and B is not.
aaB_ : give colorless product as B is functional and A is not.
So according to table 9 are purple and 7 are white.
Ratio is 9:7
AB
Ab
aB
ab
AB
AABB
AABb
AaBB
AaBb
Ab
AABb
AAbb
AaBb
Aabb
aB
AaBB
AaBb
aaBB
aaBb
ab
AaBb
Aabb
aaBb
aabb