Question

a cross is performed between a bird that is homozygous for red feathers and a bird that is homozygous for blue feathers. purple offspring result due to incomplete dominance. then, two of the purple offspring are crossed. what proportion of the offspring from the second cross will be purple? 1 in 4 2 in 4 3 in 4 4 in 4

Explanation:

Step1: Define alleles

Let R be the allele for red feathers and B be the allele for blue feathers. The cross between homozygous red - feathered (RR) and homozygous blue - feathered (BB) birds gives purple offspring (RB) due to incomplete dominance.

Step2: First cross result

The first cross (RR x BB) gives all RB (purple) offspring.

Step3: Second - cross setup

When two purple (RB) birds are crossed, the Punnett - square analysis is used. The possible gametes from each purple bird are R and B. The Punnett - square has the following combinations: RR:RB:BB = 1:2:1.

Step4: Determine purple proportion

The genotypes RR (red), RB (purple), and BB (blue). The proportion of purple (RB) offspring from the cross of two purple birds is $\frac{2}{4}=\frac{1}{2}$.

Answer:

2 in 4