The allele for pea comb (P) in chickens in completely dominants to the allele for single comb(p). The alleles for black feather colour (B) and white feather colour (B') shows codominance, so that BB' individuals posses blue feathers. If chickens heterozygous for both pairs of genes are mated, what proportion of offspring are expected to be pea combed and white feathered?

Options

A. `9//16`
B. `3//16`
C. `1//16`
D. `2//16`

Answer

To solve the problem, we need to determine the proportion of offspring that are expected to be pea combed (P) and white feathered (B') when chickens heterozygous for both traits are mated.

### Step-by-Step Solution:

1. **Identify the Genotypes of the Parents**:
- The parents are heterozygous for both traits. Therefore, their genotypes will be:
- For comb type: Pp (pea comb)
- For feather color: BB' (blue feathers)

2. **Determine the Gametes Produced by Each Parent**:
- Each parent can produce the following gametes:
- Parent 1 (PpBB'): PB, PB', pB, pB'
- Parent 2 (PpBB'): PB, PB', pB, pB'

3. **Set Up a Punnett Square**:
- Create a 4x4 Punnett square to determine the combinations of the gametes from both parents.

4. **Fill in the Punnett Square**:
- The combinations will be:
- PB x PB = PPBB' (pea comb, blue feathers)
- PB x PB' = PPB'B' (pea comb, white feathers)
- PB x pB = PpBB' (pea comb, blue feathers)
- PB x pB' = PpB'B' (pea comb, white feathers)
- pB x PB = PpBB' (pea comb, blue feathers)
- pB x PB' = PpB'B' (pea comb, white feathers)
- pB x pB = ppBB' (single comb, blue feathers)
- pB x pB' = ppB'B' (single comb, white feathers)

5. **Count the Phenotypes**:
- From the combinations, we can summarize the phenotypes:
- Pea comb and blue feathers (PPBB', PpBB'): 6
- Pea comb and white feathers (PPB'B', PpB'B'): 2
- Single comb and blue feathers (ppBB'): 2
- Single comb and white feathers (ppB'B'): 2

6. **Calculate the Proportion**:
- Total offspring = 12 (6 + 2 + 2 + 2)
- Proportion of offspring that are pea combed and white feathered = Number of pea combed and white feathered / Total offspring = 2/12 = 1/6.

### Final Answer:
The proportion of offspring expected to be pea combed and white feathered is **1/6**.