Alright, let's go through the problem step-by-step to determine the proportion of purple offspring when two purple birds, resulting from a cross of a homozygous red-feathered bird and a homozygous blue-feathered bird, are crossed.
### Initial Cross:
1. Parents:
- Homozygous red (genotype RR)
- Homozygous blue (genotype BB)
Since this scenario involves incomplete dominance, the result of crossing a homozygous red bird (RR) with a homozygous blue bird (BB) will produce heterozygous offspring (RB), which appears purple.
### Second Cross (F1 Generation Cross):
2. F1 Generation:
- Each F1 bird has genotype RB (purple).
When two F1 heterozygous purple birds (RB) are crossed, the possible genotypic combinations in their offspring follow Mendelian genetics for incomplete dominance.
### Punnett Square for RB x RB:
```
| R | B |
R | RR | RB |
B | RB | BB |
```
### Offspring Genotypes and Proportions:
- RR: Homozygous red (1 part)
- RB: Heterozygous purple (2 parts)
- BB: Homozygous blue (1 part)
3. Proportion Calculation:
- Total parts = 1 (RR) + 2 (RB) + 1 (BB) = 4 parts
- The proportion of heterozygous purple (RB) offspring = 2 parts out of 4 parts
4. Result:
- The proportion of purple offspring from the second cross is [tex]\( \frac{2}{4} \)[/tex].
Given the options:
1 in 4
2 in 4
3 in 4
4 in 4
The correct answer is: 2 in 4.
