A chromatid is one-half of two identical copies of a replicated chromosome. During cell division, the identical copies are joined together at the region of the chromosome called the centromere.Joined chromatids are known as sister chromatids. Once the joined sister chromatids separate from one another in anaphase of mitosis, each is known as a daughter chromosome.Chromatids are formed from chromatin fibers.Bailey, Regina. "Chromatid." ThoughtCo, Apr. 17, 2017.