Chromatids are the daughter strands of a duplicated chromosome which are joined by a single centromere. When the centromere divides, the chromatids become separate chromosomes.[1]
Each of the two daughter chromatids contains the same DNA and chromatin protein as its original chromosome. But in meiosis, crossing over (exchanges) take place between two of the non-sister chromatids. This has profound consequences: it produces genetic recombination, and increases the variability of gametes.