Q.Two key events take place, during S phase in animal cells, DNA replication and duplication of centriole. In which parts of the cell do events occur?

S phase in animal cells is a stage where two separate duplication events happen at the same time, but in two different parts of the cell.

• During S phase, DNA replication proceeds inside the nucleus, where the chromosomes themselves are copied.
• At the very same time, the centriole is duplicating out in the cytoplasm, entirely separate from the nucleus. …

S phase, the Synthesis phase of interphase, is specifically the period during which DNA synthesis, or replication, occurs, doubling the amount of DNA per cell while leaving the chromosome number unchanged. This is the well-known headline event of S phase, but it is not the only thing happening at this stage in an animal cell.

• DNA replication occurs in the nucleus, since this is where the chromosomes themselves are located and where they are copied.
• Centriole duplication occurs in the cytoplasm, entirely separately from the nucleus — while DNA replication is proceeding inside the nucleus, the centriole is described as duplicating out in the cytoplasm at the same time. …

Step 1 — Recall that S phase runs two duplication events in parallel, not sequentially.

Step 2 — Locate DNA replication: it copies the chromosomes, which reside in the nucleus, so it occurs in the nucleus. …