Barr body in mammals represent

Options

A. All the heterochromatin in male and female cells
B. The Y-chromosome in somatic cells of male
C. All the heterochromatin in female cells
D. One of the two X-chromosomes in somatic cells of females

Answer

**Step-by-Step Solution:**

1. **Understanding Barr Body**: The Barr body is defined as the inactivated X chromosome found in the somatic cells of female mammals. In females, who have two X chromosomes (XX), one of these X chromosomes becomes inactivated during early embryonic development.

2. **Identifying the Characteristics**: The inactivated X chromosome, or Barr body, is characterized as tightly coiled and appears as visible heterochromatin under a microscope. This coiling prevents the expression of genes on that X chromosome.

3. **Correct Answer Identification**: The question asks what the Barr body represents. The correct answer is that it represents one of the two X chromosomes in the somatic cells of females. Therefore, the correct option is that the Barr body is one of the two X chromosomes in the somatic cells of females.

4. **Eliminating Incorrect Options**:
- The option stating that it is all heterochromatin in male and female cells is incorrect because Barr bodies are specific to females.
- The option claiming it is the Y chromosome in somatic cells of males is incorrect since males have one X and one Y chromosome, and the Barr body is related to the X chromosome.
- The option stating it is all heterochromatin in female cells is also incorrect as it specifically refers to the inactivated X chromosome.

5. **Final Conclusion**: The Barr body represents the inactivated X chromosome in the somatic cells of females, confirming that the correct answer is option B.