Question

How does the cell cycle start off?

Answer 1

A new cell arises when one cell divides or when two cells, like a sperm and an egg cell, fuse. Either event sets off a cell-replication program that is encoded in the DNA and executed by proteins.

Answer 2

Entry to the cycle is made in Gap 1 (G1) phase and this is followed in sequence by a DNA synthesis (S) phase, Gap 2 (G2) phase, and Mitosis (M). After mitosis (M) some cells enter the G1 phase of a new cell cycle whilst others may diverge at the start of G1 into a phase called Gap 0 (zero)