What will be the number of linkage groups in a cell having 2n=20?

Options

A. 15
B. 40
C. 10
D. 4

Answer

To determine the number of linkage groups in a cell with a diploid number of chromosomes (2n = 20), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Diploid Number**: The notation 2n = 20 indicates that the organism is diploid, meaning it has two sets of chromosomes. Here, "n" represents the haploid number of chromosomes.

2. **Calculate the Haploid Number**: To find the haploid number (n), we divide the diploid number by 2:
\[ n = \frac{2n}{2} = \frac{20}{2} = 10 \]
Therefore, the haploid number of chromosomes is 10.

3. **Linkage Groups Definition**: A linkage group is defined as a group of genes that are located on the same chromosome and tend to be inherited together. Each chromosome represents one linkage group.

4. **Determine the Number of Linkage Groups**: Since each chromosome corresponds to one linkage group, the number of linkage groups in a haploid cell is equal to the haploid number of chromosomes. Thus, for this organism:
\[ \text{Number of linkage groups} = n = 10 \]

5. **Conclusion**: Therefore, in a cell with 2n = 20 chromosomes, there are 10 linkage groups.

### Final Answer:
The number of linkage groups in a cell having 2n = 20 is **10**.

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