B
A short interphase is followed by a long mitotic phase
C
$G_2$ phase follows mitotic phase
D
In $G_1$ phase DNA content is double the amount of DNA present in the original cell
The answer is A.
Solution
The cell cycle consists of interphase ($G_1$, S and $G_2$ phases) followed by the M phase (mitosis). DNA replication takes place in the S (synthesis) phase. The DNA content doubles from 2C to 4C, while the chromosome number stays the same; true. Interphase is long (about 95 percent of the cycle) and the M phase is short (in a 24 hour human cell cycle, mitosis lasts about 1 hour). So the second statement is false. $G_2$ follows the S phase, not the mitotic phase; $G_1$ follows mitosis. So the third statement is false. In $G_1$ the DNA content is 2C, the same as in the original cell, not double. So the fourth statement is false. So in the somatic cell cycle, DNA replication takes place in the S phase.
ConceptS phase and DNA replication
Phases of cell cycle in past papers
4 questions from this chapter have appeared across 4 exam years.
