Ring chromosome

As a ring chromosome, circular chromosome or chromosome ring refers to a ring-shaped chromosome. In prokaryotes, in which only a nucleoid ( bacterial chromosome ) is present, this generally has a circular shape. In mammals, it is, however, a structure anomaly associated with the loss of chromosome material.

Anomaly

Ring chromosomes arise when it comes during cell division to two breaks in the chromatids of a chromosome, so that the telomeric sequences are lost. Thereby can not be recognized as such, the ends of the linear chromosome by the DNA repair mechanisms. As a consequence of the breaking locations can be connected so that they form a ring. Tear this ring during mitosis, chromosome material can be lost ( deletion ).

In humans, lead ring chromosomes, which leads to deletions of syndromes whose symptoms and course are different.

Examples are the 18 -R syndrome ring chromosome 13 's syndrome, chromosome 15, the ring and the ring syndrome chromosome 20 syndrome.