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 question regarding the DNA content in the somatic cell of an animal at the end of the G2 phase, we will follow these steps:

### Step-by-step Solution:

1. **Identify the DNA content in the gamete**:
The question states that the nucleus of a gamete has 5 picograms (pg) of DNA. Since gametes are haploid, this means they contain half the amount of DNA compared to diploid somatic cells.

2. **Determine the DNA content in the diploid somatic cell**:
When two gametes (one from each parent) fuse during fertilization, they form a diploid zygote. Therefore, the total DNA content in the zygote will be the sum of the DNA from both gametes:
\[ \text{DNA in zygote} = 5 \text{ pg (from one gamete)} + 5 \text{ pg (from another gamete)} = 10 \text{ pg} \]

3. **Understand the cell cycle phases**:
- The cell cycle consists of several phases: G1, S, G2, and M.
- After the G1 phase, the cell enters the S phase, where DNA replication occurs.

4. **Calculate the DNA content after S phase**:
During the S phase, the DNA content is replicated. Thus, the DNA content in the diploid cell after the S phase will be:
\[ \text{DNA after S phase} = 10 \text{ pg} \times 2 = 20 \text{ pg} \]

5. **Determine the DNA content at the end of G2 phase**:
The DNA content remains the same from the end of the S phase through the G2 phase, as no further replication occurs. Therefore, at the end of the G2 phase, the DNA content will still be:
\[ \text{DNA at G2 phase} = 20 \text{ pg} \]

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

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