Question

If a mammalian cell completes one cell cycle in \(24\) hours and the S phase lasts \(8\) hours, what fraction of the cell cycle is spent in S phase?

• A. \(\dfrac{1}{2}\)
• B. \(\dfrac{1}{3}\)
• C. \(\dfrac{1}{4}\)
• D. \(\dfrac{1}{8}\)

Hint:

The fraction of time spent in any phase is \[ \boxed{ \frac{\text{Duration of the phase}}{\text{Total cell cycle duration}}. } \] Here, \[ \boxed{ \frac{8}{24}=\frac13. } \]

Answer 1

The Correct Option is B

Step 1: Determine the total duration and S phase duration. Given, \[ \text{Total cell cycle}=24\ \text{hours}, \] and \[ \text{S phase}=8\ \text{hours}. \]

Step 2: Calculate the required fraction. The fraction of the cell cycle spent in S phase is \[ \frac{\text{S phase duration}}{\text{Total cell cycle duration}} = \frac{8}{24} = \frac13. \] Hence, \[ \boxed{\frac13} \] is the required fraction. Therefore, \[ \boxed{(B)} \] is the correct answer.