Gene A converts compound A (green) to compound B (blue). Gene B converts compoun
ID: 311031 • Letter: G
Question
Gene A converts compound A (green) to compound B (blue). Gene B converts compound B to compound C (red). These compounds determine the color of the individual. In a self cross of AaBb individuals, what proportion of blue to green offspring should be seen?
I know I have seen this question posted here in a variety of forms but what is particularly troubling to me about this question is:
1. How exactly should I approach this question?
2. How can there be ANY green individuals if gene A converts green to blue?
3. How is there a complete lack of red individuals if Gene B converts blue to green
Explanation / Answer
Answer:
1. How exactly should I approach this question?
AaBb x AaBb
Presence of both dominant A and B = Red
Presence of A and b = Blue
Presence of a and B = Green
AB
Ab
aB
ab
AB
AABB (red)
AABb (red)
AaBB (red)
AaBb (red)
Ab
AABb (red)
AAbb (Blue)
AaBb (red)
Aabb (Blue)
aB
AaBB (red)
AaBb (red)
aaBB (green)
aaBb (green)
ab
AaBb (red)
Aabb (Blue)
aaBb (green)
aabb (green)
3 blue: 4 green
==
AB
Ab
aB
ab
AB
AABB (red)
AABb (red)
AaBB (red)
AaBb (red)
Ab
AABb (red)
AAbb (Blue)
AaBb (red)
Aabb (Blue)
aB
AaBB (red)
AaBb (red)
aaBB (green)
aaBb (green)
ab
AaBb (red)
Aabb (Blue)
aaBb (green)
aabb (green)
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