In which phase each chromosome replicates to produce two sister chromatids

Each chromosome replicates to produce two sister chromatids during the S (synthesis) phase of the cell cycle. The S phase follows the G1 (Gap 1) phase and precedes the G2 (Gap 2) phase. During S phase, the cell's DNA is replicated, resulting in the doubling of genetic material. At the end of S phase, each chromosome consists of two identical sister chromatids held together at a region called the centromere. These sister chromatids will later be separated during mitosis or meiosis to ensure that each daughter cell receives an identical copy of the genetic material.