Final answer:
Chromosomes are replicated during the S phase of interphase, resulting in the formation of sister chromatids that are held together at the centromere. This ensures that each new cell receives an identical set of genetic information.
Step-by-step explanation:
Chromosomes are replicated during the S phase of interphase. This process results in the formation of identical pairs of DNA molecules, known as sister chromatids, that are held together at the centromere. The replication of chromosomes is essential for cell division and ensures that each new cell receives an identical set of genetic information.