Question

What is required for entry into the S phase (start DNA replication)?

Answer 1

Entry into the S phase of DNA replication requires certain factors and checkpoints, such as the G1 checkpoint and the G2 checkpoint.

Step-by-step explanation:

Entry into the S phase of DNA replication requires certain factors and checkpoints.

1. The G1 checkpoint ensures that the cell is ready to proceed to the S phase. It checks if the cell has accumulated enough proteins necessary for replication, such as DNA polymerases and helicases.
2. The G2 checkpoint verifies if the DNA replication in the S phase has been completed properly and if the replicated DNA is undamaged.
3. During the S phase, DNA replication occurs and identical pairs of DNA molecules, called sister chromatids, are formed.