The genome of onion has 8 chromosomes (n=8). In a root tip cell undergoing anaphase the number of chromosomes will be

Options

A. 8
B. 16
C. 32
D. Indeterminate

Answer

To solve the question regarding the number of chromosomes in an onion root tip cell undergoing anaphase, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Chromosome Number**: The genome of the onion is given as n = 8. This means that the haploid number of chromosomes is 8.

2. **Determine the Diploid Number**: Since the onion is a diploid organism, we can calculate the diploid number of chromosomes (2n).
\[ 2n = 2 \times 8 = 16 \]
Thus, the diploid number of chromosomes in the onion is 16.

3. **Identify the Cell Type**: The question specifies that we are looking at a root tip cell. Root tip cells are part of the growing region of the plant and are actively dividing.

4. **Understand the Cell Cycle**: During the cell cycle, specifically during the S phase, DNA replication occurs. This means that each chromosome is duplicated, resulting in two sister chromatids for each chromosome.

5. **Analyze the Anaphase Stage**: Anaphase is the stage of mitosis where the sister chromatids are separated and pulled to opposite poles of the cell. At this point, the total number of chromatids is double the number of chromosomes present in the diploid state.

6. **Calculate the Number of Chromosomes During Anaphase**: Since there are 16 chromosomes (from the diploid state), during anaphase, each of these chromosomes has been replicated into two sister chromatids:
\[ \text{Total Chromatids} = 16 \text{ (original chromosomes)} \times 2 = 32 \]
Therefore, during anaphase, the onion root tip cell will have 32 chromatids.

7. **Conclusion**: The number of chromosomes during anaphase in the onion root tip cell is 32.

### Final Answer:
The number of chromosomes in the onion root tip cell undergoing anaphase is **32**.

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