The chromosomal entities have vital role in the cellular life cycle and in the regulation of gene expression the chromatin conformation has its fundamental toll. The centromeric recurrence successions presents sticky-locations for the specific kinetochore proteins and the attenuation of telomeric repeat length through propagation sets confines to the duration of the life of human cells. Usually the two linear sister chromatids resulted of DNA replication arrange themselves in an analogous configuration so that proportioned division happens at the shift of metaphase to anaphase. Conversely, a transformation in morphology from straight to spherical may entirely interrupt this succession of events. Ring chromosomes have been found in all human chromosomes. Infrequently, the ring chromosomes are found as legitimate eccentricities in very early life with developmental anomalies. They may come up as acquired genetic deformity in cells ranging from tumors or leukemia’s. Therefore it can be said that the atypical ring chromosomes are the consequence of cleavage at the terminals of arms of both the chromosomes with consequent union of the wrecked ends to bring into being an incessant ring. Broadly there aretwo types of ring chromosomes. In one category, the nonsupernumerary loop substitutes one of the ordinary homolog’s with a 46 (r) karyotype. It may be associated with a loss of genetic substance. Also sometimes the terminals of wrecked chromosomes are seen where the telomere of one chromosome arm mingle with the telomere of its opposite chromosome arm. Such mingling may occur at subtelomeric level also. However unusual, these intact rings in with no considerable loss of genetic material is evident, is along with individuals having ordinary phenotypes. In the other subtype it is said to have the supernumerary ring. It is frequently petite with peripherally placed centromere commonly in lieu of partial trisomies. A very few instances are reported where ring chromosomes pass successively from one generation to other. Mostly it is found to have instance crop up. Chromosome reformation ends up either in the configuration of a chimaeric gene or an altered oncogene expression with persuasive transforming potential. The fusion in chronic myeloid leukemia is a classic example of this type of ring chromosome.
Keywords:Ring Chromosome; Human Chromosome; Chromatin; Centromere; Telomere; Oncogene.
Review Article
P. 11-15
