Amount of cellular DNA increases during

Options

A. Cytokinesis
B. Fertilization
C. Mutation
D. Respiration

Answer

To solve the question regarding when the amount of cellular DNA increases, we can analyze each option provided:

1. **Cytokinesis**: This is the process that occurs after mitosis where the cytoplasm of a parental cell divides into two daughter cells. During cytokinesis, the amount of DNA does not increase; rather, it is distributed equally between the two daughter cells. Therefore, this option does not lead to an increase in cellular DNA.

2. **Fertilization**: This is the fusion of male and female gametes (sperm and egg). Each gamete is haploid (N), meaning it contains one set of chromosomes. When they fuse during fertilization, they form a diploid zygote (2N), which contains two sets of chromosomes. This process effectively doubles the amount of DNA present, as the zygote will have a complete set of chromosomes from both parents. Therefore, this option does lead to an increase in cellular DNA.

3. **Mutation**: This refers to a change in the DNA sequence, which can occur due to various factors. While mutations can alter the DNA sequence, they do not inherently increase the total amount of DNA in a cell. Instead, they change the existing DNA. Thus, this option does not result in an increase in cellular DNA.

4. **Respiration**: This is a metabolic process where glucose and other substrates are broken down to produce energy. While respiration involves the utilization of cellular DNA for metabolic processes, it does not lead to an increase in the amount of DNA within the cell. Hence, this option is also not correct.

After analyzing all options, the correct answer is **fertilization**, as this is the process that results in an increase in the amount of cellular DNA.

### Step-by-Step Solution:
1. **Identify the processes**: Understand what each option represents in terms of cellular processes.
2. **Analyze cytokinesis**: Recognize that cytokinesis divides the cytoplasm but does not increase DNA.
3. **Examine fertilization**: Acknowledge that fertilization combines two haploid gametes to form a diploid zygote, effectively doubling the DNA.
4. **Consider mutation**: Realize that mutations change existing DNA but do not increase the total amount.
5. **Evaluate respiration**: Understand that respiration is a metabolic process that does not increase DNA quantity.
6. **Conclude**: Determine that the only process that results in an increase in cellular DNA is fertilization.