kromatidok

Kromatidok, or chromatids in English, are the identical copies of a chromosome that result from DNA replication. In a replicated chromosome, two chromatids are held together at the centromere and constitute a single chromosome until they are separated during cell division. The two chromatids of a replicated chromosome are called sister chromatids, and they contain an identical DNA sequence. They are held together by cohesion proteins and are stabilized by the centromere and kinetochore structures.

Each chromatid comprises a DNA double helix packaged with histones and other proteins. The constricted region called the centromere is the attachment site for the kinetochore, which interacts with spindle microtubules to pull chromatids apart during mitosis or meiosis II.

In mitosis, sister chromatids separate during anaphase, and each chromatid becomes an independent chromosome delivered to opposite poles. In meiosis, separation of sister chromatids occurs in meiosis II, after homologous chromosomes have been separated in meiosis I.

In meiosis I, crossing over between nonsister chromatids of homologous chromosomes can occur during prophase I, producing recombinant chromatids with new allele combinations, reducing linkage between loci.

The word kromatidok is Hungarian for chromatids.