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): During the S phase of the cell cycle, the amount of DNA per cell doubles but the chromosome number remains the same. Reason (R): During DNA replication in the S phase, the newly formed sister chromatids remain attached to each other at a common centromere. In the light of the above statements, choo
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
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
Assertion (A) is a correct statement. During the synthesis phase (S phase) of the cell cycle, DNA replication takes place. If the initial amount of DNA is denoted as 2 C , it increases to 4 C . However, there is no increase in the chromosome number; if the cell had 2n chromosomes at G ₁ , it will still have 2n chromosomes after the S phase. Reason (R) is also a correct statement and provides the correct explanation for the Assertion. The chromosome number is determined by counting the number of centromeres. During