The nucleus of a gamete of an animal has 5 pg DNA. What will be the content of DNA in the somatic cell of the same animal at the end on G2 phase ?

Options

A. 10 pg
B. 5 pg
C. 20 pg
D. 40 pg

Answer

To solve the problem, we need to determine the DNA content in a somatic cell at the end of the G2 phase, given that the nucleus of a gamete has 5 picograms (pg) of DNA.

### Step-by-step Solution:

1. **Identify the DNA content in the gamete:**
- The question states that the nucleus of a gamete has 5 pg of DNA. Gametes are haploid cells (N), meaning they contain one set of chromosomes.

2. **Determine the DNA content in somatic cells:**
- Somatic cells are diploid (2N), meaning they contain two sets of chromosomes. Therefore, the DNA content in a somatic cell can be calculated as:
\[ \text{DNA in somatic cell} = 2 \times \text{DNA in gamete} = 2 \times 5 \text{ pg} = 10 \text{ pg} \]

3. **Consider the cell cycle phases:**
- The question specifies that we are looking for the DNA content at the end of the G2 phase. The G2 phase follows the S phase, during which DNA replication occurs.

4. **Calculate the DNA content after the S phase:**
- At the end of the S phase, the DNA content in the somatic cell doubles. Since we determined that the somatic cell has 10 pg of DNA at the end of the G1 phase, after DNA replication in the S phase, the DNA content will be:
\[ \text{DNA at end of G2 phase} = 10 \text{ pg} \times 2 = 20 \text{ pg} \]

5. **Conclusion:**
- Therefore, the DNA content in the somatic cell at the end of the G2 phase is 20 pg.

### Final Answer:
The content of DNA in the somatic cell of the same animal at the end of the G2 phase is **20 picograms** (Option 3).

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