During cell growth, DNA synthesis takes place in S phase, G2 phase, G1 phase, or M phase?

Interphase is the period between two subsequent M phases and consists of three phases: G1, S phase (the period of DNA replication) and G2 phase. The G1 phase is the gap between M phase and S phase and is marked by synthesis of RNA and protein (excluding histones) and duplication of all cell content except DNA. S phase of DNA replication and cell division is followed by G2 phase during which cell double-checks the duplicated DNA content.