A male human is heterozygous for autosomal genes A and B and is also hemizygous for hemophilic gene h. What proportion of his sperms will be abh

Options

A. (a) `1//16`
B. (b) `1//4`
C. (c) `1//8`
D. (d) `1//32`

Answer

To solve the problem of determining the proportion of sperm that will carry the genotype abh from a male who is heterozygous for autosomal genes A and B and hemizygous for the hemophilic gene h, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Genotypes**:
- The male is heterozygous for genes A and B, which means he has the genotype AaBb.
- He is hemizygous for the hemophilic gene h, which means he has the genotype h (since males have one X chromosome and one Y chromosome, they only have one copy of genes on the X chromosome).

2. **Determine the Number of Alleles**:
- For gene A (Aa), there are 2 possible alleles: A or a.
- For gene B (Bb), there are also 2 possible alleles: B or b.
- For the hemophilic gene h, since it is hemizygous, the male can only pass on the h allele.

3. **Calculate the Total Number of Gametes**:
- The formula for calculating the number of different gametes is \(2^n\), where \(n\) is the number of heterozygous gene pairs.
- In this case, there are 2 heterozygous pairs (A and B), so \(n = 2\).
- Therefore, the total number of gametes = \(2^2 = 4\).

4. **List All Possible Gametes**:
- The possible combinations of gametes from AaBb (considering the hemizygous h) are:
- ABh
- Abh
- aBh
- abh
- Thus, we have 4 different gametes.

5. **Identify the Desired Gamete**:
- We are interested in the gamete that carries the genotype abh.
- From our list of possible gametes, we can see that "abh" is one of the four combinations.

6. **Calculate the Proportion**:
- The proportion of sperm that will carry the genotype abh is the number of gametes with the abh genotype divided by the total number of gametes.
- There is 1 gamete with the abh genotype out of a total of 4 gametes.
- Therefore, the proportion is \( \frac{1}{4} \).

### Final Answer:
The proportion of his sperm that will carry the genotype abh is \( \frac{1}{4} \).

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