Chromatid is a replica of a CHROMOSOME that develops in preparation for cell division. Chromatids are “sister” pairs of each chromosome that contain identical genetic material. They remain attached to each other at the CENTROMERE until cell division. When the mother cell divides, the sister chromatids separate at the centromere and migrate into the new daughter cells, forming the chromosome pairs for the new cells.
Though minor variations are normal and frequently occur without causing problems because they affect relatively few cells, errors in chromatid replication and separation affect many or all cells and can be responsible for CHROMOSOMAL DISORDERS such as DOWN SYNDROME.
For further discussion of chromatids within the context of the structures and functions of genetics, please see the overview section “Genetics and Molecular Medicine.”