The meiocytes of a dog contain 78 chromosomes. The number of chromosomes present in the zygote stage after fertilisation in a dog will be

Options

A. 19
B. 39
C. 78
D. 156

Answer

To solve the question regarding the number of chromosomes present in the zygote stage after fertilization in a dog, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chromosome Count in Meiocytes**:
The problem states that the meiocytes of a dog contain 78 chromosomes. Meiocytes are diploid cells, which means they contain two sets of chromosomes.

2. **Understand the Process of Meiosis**:
Meiocytes undergo meiosis to produce gametes (sperm and egg cells). During meiosis, the diploid meiocytes divide to form haploid gametes.

3. **Calculate the Number of Chromosomes in Gametes**:
Since the meiocytes are diploid (2n), and they contain 78 chromosomes, the number of chromosomes in each haploid gamete (n) will be half of that:
\[ n = \frac{78}{2} = 39 \]
Therefore, each gamete contains 39 chromosomes.

4. **Fertilization Process**:
During fertilization, a sperm cell (from the male) and an egg cell (from the female) fuse together to form a zygote. The zygote will have the combined chromosome count from both gametes.

5. **Calculate the Number of Chromosomes in the Zygote**:
Since each gamete has 39 chromosomes, the zygote will have:
\[ \text{Total chromosomes in zygote} = 39 + 39 = 78 \]
Thus, the zygote will also have 78 chromosomes.

6. **Conclusion**:
The number of chromosomes present in the zygote stage after fertilization in a dog is 78.

### Final Answer:
The number of chromosomes present in the zygote stage after fertilization in a dog is **78**.

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