Students in a biology lab isolated cells in various phases of the cell cycle. A population of cells that have 1 1/2 times the DNA of G1 phase cells was most likely isolated from which of the following parts of the cell cycle?

Question

in the M phase
between the G1 and S phases
in the G2 phase
in the S phase

Answer 1

Cells that have 1 1/2 times the DNA of G1 phase cells are most likely isolated from the S phase of the cell cycle.

During the G1 phase, cells have a certain amount of DNA (let's denote it as 1 unit), and during the S phase, DNA replication occurs, resulting in cells that contain 2 units of DNA by the end of the S phase. However, at any point during the S phase, the cells are in the process of duplicating their DNA, meaning they will have an intermediate amount of DNA — which is exactly 1 1/2 times the amount present in G1 cells.

Therefore, the correct answer is in the S phase.