What are sister chromatids?

Sister chromatids are defined as two identical copies of a single chromosome that are connected by a centromere. During the S phase of the cell cycle, when DNA is replicated, each chromosome is duplicated, resulting in a pair of sister chromatids. These chromatids are genetically identical to each other because they originate from the same parental chromosome.

This structure is crucial during cell division processes such as mitosis and meiosis. During mitosis, sister chromatids separate to ensure that each new daughter cell receives an identical set of chromosomes. In meiosis, while crossing over can occur and create genetic diversity, the individual sister chromatids themselves remain identical until separated during the second division.

Understanding this concept is fundamental in genetics and cellular biology as it lays the groundwork for more complex topics like inheritance, genetic variation, and the behavior of chromosomes during cell division.