What is the relationship between sister chromatids?

Sister chromatids are indeed identical copies of a single chromosome that are joined together at a region known as the centromere. This occurs during the S phase of the cell cycle when DNA is replicated, leading to two identical copies of the chromosome. Each sister chromatid contains the exact same genetic information, ensuring that when the cell divides during mitosis, each new daughter cell receives a complete set of chromosomes.

Given that sister chromatids arise from the duplication of a single chromosome, they should not be considered distinct chromosomes, as they retain the same genetic information and are not separate entities. Homologous chromosomes, on the other hand, consist of pairs of chromosomes—one inherited from each parent—that may contain different alleles for the same genes. Thus, describing sister chromatids as homologous chromosomes would be misleading. Additionally, the term "different chromosomes with similar genes" would imply that they are not identical copies, which contradicts the definition of sister chromatids. Therefore, identifying sister chromatids as identical copies of a chromosome is accurate and aligns with their role in cell division.