Question

Punnett squares are used to show possible combinations of alleles or to predict the probability of a trait occurring in offspring. A parakeet that is heterozygous for blue feathers (dominant) is crossed with a parakeet that is homozygous for white feathers (recessive).

A parakeet with white feathers. A parakeet with blue feathers.

According to the Punnett square for this cross, what percentage of offspring is predicted to have blue feathers?
25 percent
50 percent
75 percent
100 percent

Answer 1

To determine the percentage of offspring that will have blue feathers from the cross between a heterozygous blue-feathered parakeet (Bb) and a homozygous white-feathered parakeet (bb), we can create a Punnett square.

1. **Define the alleles**:
- B = blue feathers (dominant)
- b = white feathers (recessive)

2. **Parakeet genotypes**:
- Heterozygous blue (Bb)
- Homozygous white (bb)

3. **Set up the Punnett square**:

```
B | b
-----------------
b | Bb | bb |
-----------------
b | Bb | bb |
-----------------
```

4. **Analyze the results**:
- The offspring combinations are:
- Bb (blue feathers)
- Bb (blue feathers)
- bb (white feathers)
- bb (white feathers)

This results in:
- 2 Bb (blue feathers)
- 2 bb (white feathers)

5. **Calculate the percentages**:
- Total offspring = 4
- Percentage with blue feathers (Bb) = (2 / 4) × 100 = 50%

Therefore, the predicted percentage of offspring with blue feathers is **50 percent**.