NEETBotanyCell Cycle and Cell Division
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The amount of DNA per cell doubles during the synthesis (S) phase, but the chromosome number remains the same. Reason (R): Karyokinesis strictly follows the G2 phase to ensure the equal distribution of the duplicated sister chromatids. In the light of the above statements, choose the most appropria
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
Step-by-step solution
Assertion (A) is correct because during the S phase, DNA replication occurs, causing the DNA content to double (e.g., from 2C to 4C). However, the chromosome number remains unchanged because the newly formed sister chromatids remain attached at a single centromere. Reason (R) is also correct as karyokinesis (nuclear division) occurs during the M phase, which follows the G2 phase, and it results in the separation and equal distribution of these chromatids. However, (R) is not the correct explanation for (A). The chr