Assertion: Senescence is the time when age associated defects are manifested.
Reason: Certain genes may be undergoing sequential switching on and off during one's life.

Options

A. If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
B. If both Assertion and Reason are true and the Reason is not the correct explanation of the Assertion.
C. If Assertion is true but the Reason is false.
D. If both Assertion and Reason are false.

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Assertion**: The assertion states that "Senescence is the time when age-associated defects are manifested." This means that senescence refers to the period in an organism's life when the signs of aging and related defects become evident.

2. **Understanding the Reason**: The reason provided is that "Certain genes may be undergoing sequential switching on and off during one's life." This indicates that the expression of certain genes changes throughout an individual's life, which can influence the aging process and the manifestation of age-related defects.

3. **Analyzing the Relationship**: To determine the relationship between the assertion and the reason, we need to evaluate if both statements are true and if the reason explains the assertion.

4. **Evaluating the Truth of the Assertion**: The assertion is indeed true. Senescence is recognized as a phase of life where aging signs appear, leading to various defects associated with old age.

5. **Evaluating the Truth of the Reason**: The reason is also true. The switching on and off of genes throughout life can affect the aging process and the timing of when defects become apparent.

6. **Determining the Explanation**: The reason provides a biological basis for the assertion. The sequential switching of genes can lead to the manifestation of age-related defects, supporting the idea that senescence is linked to genetic factors.

7. **Conclusion**: Since both the assertion and reason are true, and the reason correctly explains the assertion, we conclude that the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

**Final Answer**: Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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