Question

Some chemotherapy drugs act by attaching themselves to the growing strand of a DNA molecule, thus preventing its replication. Cells on which phase of the cell cycle would be affected by this drug?

Answer 1

is when the cell is on the S phase.

S-Phase is the part of cell cycle when the DNA is replicating, occurring between G1 and G2 phase

If the replication is somehow prevented, the drugs is most likely affecting the S-Phase

Answer 2

The answer is S phase.

If drugs prevent DNA replication which occurs in the S phase. That means that the S phase will be affected by these drugs.