Chromatid
In the diagram, (1) refers to a chromatid: one-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. A chromatid (Greek khrōmat- 'color' + -id ) is one copy of a newly copied chromosome which is still joined to the original chromosome by a single centromere. Before replication, one chromosome is composed of one DNA molecule. Following replication, each chromosome is composed of two DNA molecules; in other words, DNA replication itself increases the amount of DNA but does not (yet) increase the number of chromosomes. The two identical copies—each forming one half of the replicate...