DNA synthesis does not exist and what you are probably looking for cell reproduction or cell mitosis. In cell mitosis there are 6 phases which is interphase when the cell makes the centrioles and begins preparing for the duplication of DNA. In prophase DNA is copied from the nucleus, metaphase aligns the DNA for the split, anaphase separates the DNA and centrioles, and in telophase the cell splits into two separate DNA and centriole developing into 2 new cells.
DNA synthesis refers to the creation of new DNA molecules. It takes place during the synthesis phase (S Phase) of cell reproduction.
S phase - for synthesis
DNA is replicated in the S phase; synthesis phase.
Interphase
S-phase of interphase
Because protein synthesis is taking place.
Within the Cell cycle, Dna synthesis occurs during the S [synthesis] phase.
The DNA is synthesized during the S-phase of the cell's Interphase (G1, S, G2)... That is why it is called the "S" phase-- standing for the word "synthesis".
DNA replication
Interphase (synthesis)
Growth Phase permutes to the Dna Synthesis Phase; a brief G2 Phase is followed by M - Mitosis - Phase which results in the formation of two Daughter Cells.
Synthesis phase or "S phase" occurs during the interphase of a cell cycle between the G1 and G2 stages. During synthesis phase, DNA molecules "unzip" and each old strand attracts free nucleotides forming complementary new strands, leaving two strands of DNA identical to the original strand of DNA.