Human males are hemizygous for

Options

A. Y-linked gene
B. X-linked genes
C. X,Y-linked genes
D. X-linked and -linked genes

Answer

**Step-by-Step Solution:**

1. **Understanding Hemizygosity:**
- Hemizygous refers to the condition where an individual has only one copy of a gene instead of the usual two copies (homozygous). This is commonly seen in males for genes located on the X chromosome.

2. **Identifying Male Chromosomal Composition:**
- In humans, males have one X chromosome and one Y chromosome (XY), while females have two X chromosomes (XX). This means that males have only one copy of the X chromosome.

3. **Analyzing the Options:**
- The question provides four options: Y-linked gene, X-linked gene, X-Y linked gene, and X-linked and Y-linked gene.
- Since males have only one X chromosome, they are hemizygous for genes located on the X chromosome.

4. **Determining the Correct Answer:**
- Males are hemizygous for X-linked genes because they have only one X chromosome. They do not have a second X chromosome to provide a second allele for comparison.
- Y-linked genes are not considered hemizygous in this context because hemizygosity specifically refers to the X chromosome in males.

5. **Conclusion:**
- Therefore, the correct answer is that human males are hemizygous for **X-linked genes**.

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