The ratio of number of chromosomes in a human zygote and a human sperm is :

Options

A. `2:1`
B. `3:1`
C. `1:2`
D. `1:3`

Answer

To determine the ratio of the number of chromosomes in a human zygote to that in a human sperm, follow these steps:

### Step-by-Step Solution:

1. **Understand the Chromosome Number in Humans**:
- Humans have a total of 46 chromosomes. This number is referred to as the diploid number (2n), which is found in somatic (body) cells.

2. **Identify the Chromosome Number in a Zygote**:
- A zygote is formed when a sperm cell (male gamete) fertilizes an egg cell (female gamete). Since both the sperm and the egg contribute half of the chromosomes, the zygote will have the full set of chromosomes.
- Therefore, the number of chromosomes in a human zygote is 46 (2n).

3. **Identify the Chromosome Number in a Sperm Cell**:
- Sperm cells are gametes and have only half the number of chromosomes compared to somatic cells. Thus, the number of chromosomes in a human sperm is 23 (n).

4. **Calculate the Ratio**:
- Now, we can set up the ratio of chromosomes in a zygote to that in a sperm:
- Ratio = Number of chromosomes in zygote : Number of chromosomes in sperm = 46 : 23

5. **Simplify the Ratio**:
- To simplify the ratio, divide both numbers by 23:
- 46 ÷ 23 = 2
- 23 ÷ 23 = 1
- Therefore, the simplified ratio is 2 : 1.

### Final Answer:
The ratio of the number of chromosomes in a human zygote to that in a human sperm is **2 : 1**.

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