In case of mice coat colour, two genes are responsible for colour of the hair, Gene A is responsible for distribution of pigments on shaft of hair. Wild type allele of 'A' produces a yellow band on dark hair shaft (agouti), whereas recessive allele produces no yellow band. There is another allele of A, known as A, which is embryonic lethal in homozygous condition only. In an experiment, two yellow mice were crossed to obtain a progeny of 6 pups. What would be the most probable number of agouti mice among them?

Options

A. 0
B. 2
C. 4
D. None of the above

Explanation

To solve the problem, we need to analyze the genetic inheritance of coat color in mice, focusing on the alleles of gene A.

### Step-by-Step Solution:

1. **Identify the Alleles**:
- The wild type allele of gene A (let's denote it as A) produces a yellow band on the dark hair shaft (agouti).
- The recessive allele (a) does not produce a yellow band.
- There is also an embryonic lethal allele (A) that is lethal in homozygous condition (AA).

2. **Determine the Genotype of the Parents**:
- We have two yellow mice. Since yellow is produced by the presence of at least one dominant allele (A), the genotypes of the yellow mice can be either Aa or AA. However, since AA is lethal, both yellow mice must be Aa.

3. **Set Up the Punnett Square**:
- We will set up a Punnett square for the cross between two Aa mice.
- The possible gametes from each parent are A and a.
- The Punnett square will look like this:

```
A | a
----------------
A | AA | Aa
----------------
a | Aa | aa
```

4. **Analyze the Offspring**:
- From the Punnett square, the genotypes of the offspring are:
- 1 AA (which is lethal and will not survive)
- 2 Aa (which will be agouti)
- 1 aa (which will not have the yellow band and will be a different color)
- Therefore, out of 4 offspring, 2 will be agouti (Aa) and 1 will be aa.

5. **Calculate the Expected Number of Agouti Mice**:
- Since AA is lethal, we only consider the surviving offspring.
- Out of the 3 surviving pups (2 Aa and 1 aa), the expected number of agouti mice is 2.

### Final Answer:
The most probable number of agouti mice among the 6 pups is **2**.