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: Determine the genotypes of the parent birds

Let \( R \) represent the allele for red feathers and \( B \) represent the allele for blue feathers. The homozygous red - feathered bird has genotype \( RR \), and the homozygous blue - feathered bird has genotype \( BB \).

Step2: Determine the genotype of the purple - feathered offspring (F1 generation)

When \( RR\times BB \), using the Punnett square (or simple allele combination), all \( F1 \) offspring have genotype \( RB \) (due to incomplete dominance, \( RB \) shows the purple phenotype).

Step3: Cross two purple - feathered (\( RB \)) offspring

When \( RB\times RB \), using the Punnett square:

Gametes of Parent 1	Gametes of Parent 2
\( R \)	\( RR \) (red)	\( RB \) (purple)
\( B \)	\( RB \) (purple)	\( BB \) (blue)

The genotypes of the \( F2 \) generation are \( RR:RB:BB = 1:2:1 \)

Answer:

B. 2 in 4