The process of duplication of genetic material is observed in interphase (or early prophase). The particular or specific stage of the eukaryotic cell cycle during which this occurs is termed the -
S or Synthesis stage
The process of duplication of genetic material or DNA content begins in S phase and is regarded as the replication stage. To produce two similar daughter cells, the complete DNA instructions in the cell must be duplicated.
In G1 phase, cells increase in size, produce RNA and synthesize protein.
In G2 phase, during the gap between DNA synthesis and mitosis, the cell continues to grow and produce new proteins.
In the G0 phase, a cell will leave the cycle and quit dividing. This may be a temporary resting period or more permanent. An example of the latter is a cell that has reached an end stage of development and will no longer divide (e.g. neuron).