A chromatid is one half of a duplicated chromosome. During the cell cycle, specifically in the S phase, DNA is replicated, resulting in two identical copies of each chromosome. Each copy is called a chromatid, and they are joined together at a region known as the centromere. When a cell divides during mitosis or meiosis, the sister chromatids are separated and distributed into the daughter cells. This ensures that each new cell receives an identical set of chromosomes, maintaining genetic consistency across generations. Chromatids play a crucial role in the accurate transmission of genetic information.