Expression of recessive genes on X- chromosome occurs in males genes on

Options

A. (a) Hemizygous condition
B. (b) Homozygous nature
C. (c) Polyzygous nature
D. (d) Inverted condition

Answer

**Step-by-Step Solution:**

1. **Understanding Chromosomal Differences**: Recognize that males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). This difference is crucial for understanding how recessive genes on the X chromosome are expressed.

2. **Defining Hemizygosity**: The term "hemizygous" refers to the presence of only one allele for a gene in a diploid organism. In males, since there is only one X chromosome, they are considered hemizygous for genes located on the X chromosome.

3. **Recessive Gene Expression**: In males, if a recessive gene is present on their single X chromosome, it will be expressed because there is no corresponding allele on the Y chromosome to mask its effect. This is different from females, who may have one normal allele that can mask the recessive allele.

4. **Example of X-Linked Disorders**: Consider X-linked genetic disorders like hemophilia. In females, they can be homozygous (both X chromosomes have the recessive allele) or heterozygous (one X chromosome has the recessive allele, and the other has a normal allele). Only in the homozygous condition will they express the disease. In contrast, males with the recessive allele on their single X chromosome will express the disease because there is no second X chromosome to provide a normal allele.

5. **Conclusion**: Therefore, the expression of recessive genes on the X chromosome occurs in males due to their hemizygous condition, which means they have only one copy of the X chromosome.

**Final Answer**: The expression of recessive genes on the X chromosome occurs in males in a hemizygous condition.

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