In a plant red fruit (R) is dominant over yellow fruit (r)… | Dihybrid Cross and Test Cross

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In a plant red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). If a plant with RRTt genotype is crossed with a plant that is rrtt

A 50% will be tall with red fruit

B 75% will be tall with red fruit

C All the offspring will be tall with red fruit

D 25% will be tall with red fruit

The answer is A.

Solution

Gametes of RRTt: RT and Rt (in equal proportion, 1/2 each).
Gametes of rrtt: rt only.
Offspring: RT $\times$ rt = RrTt (red, tall); Rt $\times$ rt = Rrtt (red, short).
So all offspring have red fruit (Rr), because the RRTt parent is homozygous for red.
For height, Tt $\times$ tt gives 1/2 Tt (tall) and 1/2 tt (short).
Ratio: 1 red tall : 1 red short.
So 50% of the offspring will be tall with red fruit.

Concept Offspring ratio from RRTt x rrtt

In a plant red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). If a plant with RRTt genotype is crossed with a plant that is rrtt

Solution

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