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. `1/4`
B. `1/8`
C. `1/32`
D. `1/16`

Answer

To solve the problem, we need to determine the proportion of sperm that will carry the genotype "abh" from a male who is heterozygous for genes A and B and hemizygous for the hemophilic gene h.

### 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, which means he has one copy of the gene on the X chromosome (X^h) and none on the Y chromosome. Thus, his genotype for the hemophilic gene can be represented as X^hY.

2. **Determine Gamete Formation**:
- For the autosomal genes A and B (AaBb), the possible gametes can be formed by combining the alleles from each gene. The combinations are:
- AB
- Ab
- aB
- ab
- Therefore, from AaBb, we can produce 4 different combinations of alleles.

3. **Combine with Hemizygous Gene**:
- Since the male is hemizygous for the hemophilic gene, we need to consider the two possible sex chromosomes:
- From the X chromosome: X^h
- From the Y chromosome: Y
- This means that the gametes can be combined with either X^h or Y.

4. **Total Gametes**:
- The combinations of the autosomal gametes with the sex chromosomes give us:
- ABX^h
- ABy
- AbX^h
- Aby
- aBX^h
- aBy
- abX^h
- aby
- Thus, we have a total of 8 different gametes.

5. **Identify the Desired Gamete**:
- We are looking for the specific gamete "abh". This corresponds to the combination of alleles:
- a (from Aa)
- b (from Bb)
- h (from X^h)
- From the list of gametes, we see that "abX^h" is one of the combinations.

6. **Calculate the Proportion**:
- Out of the 8 total gametes, only 1 of them corresponds to the "abh" genotype.
- Therefore, the proportion of sperm that will be "abh" is 1 out of 8.

### Final Answer:
The proportion of his sperms that will be abh is **1/8**.

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