When are sister chromatids created in the cell cycle?

Sister chromatids are created during the S Phase of the cell cycle, which stands for synthesis phase. This phase is essential for DNA replication, where each chromosome is duplicated to produce two identical sister chromatids. After being replicated, these chromatids remain joined at a region known as the centromere.

During G1 Phase, the cell is primarily focused on growth and preparation for DNA replication, but no sister chromatids are formed at this point. In G2 Phase, the cell has already completed DNA replication, and sister chromatids are present, but they are not created during this phase. Anaphase, on the other hand, is when the sister chromatids are pulled apart and separated to opposite poles of the cell in preparation for division. Therefore, the correct timing for the creation of sister chromatids is indeed during the S Phase.