Gene A converts compound A (red) to compound B (blue). Gene B converts compound B to compound C (green). These compounds determine the color of the individual. In a cross between a double heterozygote and an all recessive individual, what proportion of red to green offspring should be seen/1. 1:3
2. 3:1
3. 3:4
4. 4:3
5. 4:9

1:2 ( red: green)

Explanation:

Given that:

Gene A converts compound A (red) to compound B (blue);                      &

Gene B converts compound B to compound C (green).

If a cross between a double heterozygous and recessive individual occurs

i.e AaBb     ×     aabb

what proportion of red to green offspring should be seen?

So, we have the gametes of AaBb = (AB, Ab, aB, ab)

aabb = (ab, ab, ab, ab)

                     AB                    Ab                       aB                     ab

ab                 AaBb                Aabb                aaBb                   aabb

ab                 AaBb                Aabb                aaBb                   aabb

ab                 AaBb                Aabb                aaBb                   aabb

ab                 AaBb                Aabb                aaBb                   aabb

So we have four diffeerent genes:

AaBb

Aabb

aaBb

aabb

Since A converts red to blue and B converts blue to green, then AaBb = Green (since they are heterozygous for both traits)

Aabb = Blue (since A have the tendency of converting red to blue but b do not have the tendency to convert blue to green since it is recessive)

aaBb = Red (since A is not present in the first place to convert red to blue, so the gene remains red)

aabb  = Red (since A is not present in the first place to convert red to blue, so the gene remains red)

∴

4:4:8  (blue:red:green)

1:1:2    (blue:red:green)

So since the question asked for only the proportion of red to green alone; we have 1:2 ( red: green)

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