Question

The fruit fly has 8 chromosomes (2n) in each cell. During interphase of mitosis, if the number of chromosomes at G1 phase is 8, what would be the number of chromosomes after S phase?

• A. 32
• B. 8
• C. 16
• D. 4

Answer 1

The correct option is B 8

Cell cycle includes a non-dividing phase, interphase and a dividing phase, mitotic phase.

Interphase has a long duration and during this phase the cell prepares to divide by undergoing cell growth and DNA replication.

Interphase is divided into G1, S and G2 phases.

In the G1 phase, each chromosome has a single chromatid. During S phase, the DNA undergoes replication which results in duplication of the genetic material. The content of DNA gets doubled in the S phase. Hence, at the end of S phase, each chromosome will have two chromatids due to DNA replication. But there is no change in chromosome number. It remains constant.

The fruit fly has 8 chromosomes (2n) in each cell.

If the number of chromosomes at G1 phase is 8, then the number of chromosomes after S phase also will be 8.