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: -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-3: -M phase (mitosis) is usually followed by cytokinesis. S phase is the period during which DNA replication occurs.

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