Chromatid

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.
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.
Further information: Karyotype

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.[1] During the later stages of cell division these chromatids separate longitudinally to become individual chromosomes.[2]

Chromatid pairs are normally genetically identical, and said to be homozygous. However, if mutations occur, they will present slight differences, in which case they are heterozygous. The pairing of chromatids should not be confused with the ploidy of an organism, which is the number of homologous versions of a chromosome.

  1. ^ "What is a Chromatid?". About.com. Archived from the original on 3 December 2010. Retrieved 18 July 2017.
  2. ^ "Definition of CHROMATID". Merriam-Webster. Retrieved 18 July 2017.