The human chromosomes with the highest and least number of genes in them are respectively :

Options

A. chromosome 21 and Y
B. chromosome 1 and X
C. chromosome 1 and Y
D. chromosome X' and Y

Answer

To solve the question regarding which human chromosomes have the highest and least number of genes, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Chromosomes in the Options**: The question provides four options which include chromosome 21, chromosome Y, chromosome X, and chromosome 1.

2. **Research the Number of Genes in Each Chromosome**:
- **Chromosome 1**: Contains approximately 2000 to 2100 genes.
- **Chromosome 21**: Contains approximately 500 to 600 genes.
- **Chromosome X**: Contains approximately 1000 genes.
- **Chromosome Y**: Contains approximately 55 genes.

3. **Determine the Highest Number of Genes**:
- From the data gathered, chromosome 1 has the highest number of genes (2000 to 2100).

4. **Determine the Least Number of Genes**:
- Chromosome Y has the least number of genes (approximately 55).

5. **Select the Correct Option**:
- Based on the findings, the chromosome with the highest number of genes is chromosome 1, and the chromosome with the least number of genes is chromosome Y.
- Therefore, the correct answer is option 3: Chromosome 1 (highest) and Chromosome Y (least).

### Final Answer:
The human chromosomes with the highest and least number of genes in them are respectively: **Chromosome 1 and Chromosome Y**.

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