AP BIOLOGY

Detailed explanation-1: -The S phase of the cell cycle occurs before the interphase and is involved in DNA synthesis or replication. In this way, the genetic material of the cell is replicated before entering mitosis or meiosis, leaving enough DNA to divide into daughter cells. S phase is not initiated until the cell passes the G1 phase.

Detailed explanation-2: -M phase (mitosis) is usually followed by cytokinesis. S phase is the period during which DNA replication occurs.

Detailed explanation-3: -Two key events take place, during S-phase in animal cells, DNA replication and duplication of centriole.

Detailed explanation-4: -DNA replicates in the S phase of the cell cycle and initiates at specific regions in the DNA sequence known as DNA replication ‘origins’. A number of proteins participate in DNA replication and the process is subject to scrutiny by cell surveillance mechanisms called cell cycle checkpoints.

Detailed explanation-5: -During the S phase, DNA is duplicated into two sister chromatids, and centrosomes, which give rise to the mitotic spindle, are also replicated. In the G2 phase, energy is replenished, new proteins are synthesized, the cytoskeleton is dismantled, and additional growth occurs.