chromatid

thumb|In the diagram, (1) refers to a chromatid: 1-half of two identical threadlike strands of a replicated chromosome. During cell division, the identical copies (called a "sister chromatid pair") are joined at the region called the [[centromere (2). Once the paired sister chromatids have separated from one another (in the anaphase of mitosis) each is known as a daughter chromosome. The short arm of the right chromatid (3), and the long arm of the right chromatid (4), are also marked.]] thumb|220px|Schematic karyogram of the human chromosomes, showing their usual state in the G0 and G1 phase of the cell cycle. At top center it also shows the chromosome 3 pair in [[metaphase (annotated as "Meta."), which takes place after having undergone DNA synthesis which occurs in the S phase (annotated as S) of the cell cycle. During metaphase, each chromosome is duplicated into sister chromatids.]]

A chromatid (Greek khrōmat- 'color' + -id) is one half of a duplicated chromosome. Before replication, one chromosome is composed of one DNA molecule. In replication, the DNA molecule is copied, and the two molecules are known as chromatids. During the later stages of cell division these chromatids separate longitudinally to become individual chromosomes.