Practice multiple alleles with genetics problems on pigeon feather color and rabbit fur color inheritance.

Let’s solve this step by step.

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We are told that in pigeons, feather color is controlled by multiple alleles:

- B = dominant allele → red feathers
- b⁺ = recessive to B, dominant to b → blue feathers
- b = recessive → chocolate feathers

So the dominance order is:
B > b⁺ > b

That means:
- If a pigeon has at least one B, it will be red (unless it’s homozygous for something else? Wait — no, since B is dominant over both, any genotype with B will show red).
- If no B, but has b⁺, then blue.
- Only if bb (homozygous recessive), then chocolate.

Now, let’s fill out the first table: “Possible genotypes/phenotype combinations”

Genotypes listed:
1. B/B → two copies of B → phenotype: Red
2. B/b⁺ → B is dominant → phenotype: Red
3. B/b → B is dominant → phenotype: Red
4. b⁺/b⁺ → no B, so look at next: b⁺ is present → phenotype: Blue
5. b⁺/b → b⁺ is dominant over b → phenotype: Blue
6. b/b → only recessive → phenotype: Chocolate

✔ So we can fill the first table like this:

| Genotype | Phenotype |
|----------|---------------|
| B/B | Red |
| B/b⁺ | Red |
| B/b | Red |
| b⁺/b⁺ | Blue |
| b⁺/b | Blue |
| b/b | Chocolate |

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Next part:
> 1. Using a Punnett square, show a cross among a red-and heterozygous male who also carries the chocolate allele, and a blue-and heterozygous female.

First, figure out their genotypes.

Male: “red-and heterozygous” → he is red, so must have at least one B. But he’s heterozygous → so not B/B. Also, he “carries the chocolate allele” → so he has a b allele.

Since he’s red and heterozygous and carries b, his genotype must be B/b.

Female: “blue-and heterozygous” → blue means she does NOT have B (because B would make her red). Blue comes from b⁺ being present and no B. She’s heterozygous → so not b⁺/b⁺. Therefore, she must be b⁺/b.

Wait — let’s double-check:

Blue phenotype requires: no B, and at least one b⁺.

Heterozygous → so different alleles → so yes, b⁺/b is correct.

So cross: Male: B/b × Female: b⁺/b

Set up Punnett Square:

Gametes from male (B/b): B or b
Gametes from female (b⁺/b): b⁺ or b

Punnett Square:

```
| b⁺ | b
-------------------------
B | B/b⁺ | B/b
-------------------------
b | b/b⁺ | b/b
```

Note: b/b⁺ is same as b⁺/b → phenotype blue.

Now list offspring genotypes and phenotypes:

1. B/b⁺ → Red (since B is dominant)
2. B/b → Red
3. b⁺/b → Blue
4. b/b → Chocolate

So phenotypic ratio:
→ 2 Red : 1 Blue : 1 Chocolate
Or 50% Red, 25% Blue, 25% Chocolate

But the question just says “show a cross”, so probably they want the Punnett square filled and maybe the phenotypes listed.

We’ll write the results clearly.

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Now, Example 2: Color Patterns in Rabbits

Alleles given:

- C → Dark gray coat → Dominant to all
- cᶜʰ → Chinchilla pattern → Dominant to Himalayan and white
- cʰ → Himalayan pattern → Dominant to white
- c → White coat → Recessive to all

Dominance hierarchy:
C > cᶜʰ > cʰ > c

We need to fill in phenotypes for each genotype:

Given genotypes:

1. Cc → C is dominant → phenotype: Dark gray
2. cᶜʰcʰ → no C, so look at next: cᶜʰ is present → dominant over cʰ → phenotype: Chinchilla
3. cʰc → no C or cᶜʰ, so cʰ is present → dominant over c → phenotype: Himalayan

✔ Fill the table:

| Genotype | Phenotype |
|----------|---------------|
| Cc | Dark gray |
| cᶜʰcʰ | Chinchilla |
| cʰc | Himalayan |

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Final Answer:

For pigeons:

First Table:

| Genotype | Phenotype |
|----------|---------------|
| B/B | Red |
| B/b⁺ | Red |
| B/b | Red |
| b⁺/b⁺ | Blue |
| b⁺/b | Blue |
| b/b | Chocolate |

Cross: Male B/b × Female b⁺/b

Offspring:

- B/b⁺ → Red
- B/b → Red
- b⁺/b → Blue
- b/b → Chocolate

Phenotypes: 2 Red, 1 Blue, 1 Chocolate

For rabbits:

| Genotype | Phenotype |
|----------|---------------|
| Cc | Dark gray |
| cᶜʰcʰ | Chinchilla |
| cʰc | Himalayan |