A holandric gene in man causes hypertrichosis. When a man with hairy ears marrier a normal woman

Options

A. the percentage of their sons would be 100% to have hairy ear
B. half of daughters will have this trait
C. ratio of hairy eared and normal child will be 1:2
D. all correct

Answer

### Step-by-Step Solution:

1. **Understanding Hypertrichosis**:
- Hypertrichosis refers to an abnormal amount of hair growth, particularly on the ears in this context. It is caused by a holandric gene, which is located on the Y chromosome.

2. **Identifying the Parents**:
- The male parent has hypertrichosis (hairy ears) and carries the holandric gene on his Y chromosome. The female parent is normal and does not possess a Y chromosome.

3. **Genetic Contribution**:
- Since the gene for hypertrichosis is located on the Y chromosome, only males can inherit this trait from their father. Females do not inherit Y chromosomes from their fathers; they inherit X chromosomes.

4. **Offspring Analysis**:
- The male will pass on his Y chromosome to his sons, which will carry the gene for hypertrichosis. Therefore, all sons will inherit the Y chromosome with the holandric gene and will exhibit the trait (hairy ears).
- The daughters will inherit one of the X chromosomes from their father and will not inherit the Y chromosome. Thus, they will not express hypertrichosis.

5. **Conclusion**:
- All sons will have hairy ears (100% will inherit the trait), while daughters will remain normal (0% will inherit the trait).

### Final Answer:
- **100% of the sons will have hairy ears.**
- **0% of the daughters will have hairy ears.**