AP BIOLOGY

Detailed explanation-1: -S phase. In S phase, the cell synthesizes a complete copy of the DNA in its nucleus. It also duplicates a microtubule-organizing structure called the centrosome. The centrosomes help separate DNA during M phase.

Detailed explanation-2: -S phase is the period during which DNA replication occurs.

Detailed explanation-3: -The cell grows and carries out biochemical functions, such as protein synthesis, in the G1 phase. During the S phase, DNA is duplicated into two sister chromatids, and centrosomes, which give rise to the mitotic spindle, are also replicated.

Detailed explanation-4: -G1 phase together with the S phase and G2 phase comprise the long growth period of the cell cycle cell division called interphase that takes place before cell division in mitosis (M phase). During G1 phase, the cell grows in size and synthesizes mRNA and protein that are required for DNA synthesis.