Extrachromosomal Circular DNA are composed of chromatin and replicate in the nucleus of the cell during cell division. Unlike typical chromosomes, they are composed of circular fragments of DNA, up to only a few million base pairs in size and contain no centromere or telomere. Extrachromosomal Circular DNA Extrachromosomal circular DNA (eccDNA) is circular DNA found in the nuclei of plant and animal cells, including human cells, in addition to chromosomal DNA. eccDNA can be from 200 up to 5 million base pairs in length. eccDNA has been found in the nuclei of human cancer cells and shown to carry many copies of
Single-cell DNA template strand sequencing cellular processes. Briefly, pulse-chase assays allow researchers to track radioactively labelled molecules in the cell. In experiments used to study non-random chromosome assortment, stem cells are labeled or "pulsed" with a nucleotide analog that is incorporated in the replicated DNA strands. This allows the nascent stands to be tracked through many rounds of replication. Unfortunately, this method is found to have poor resolution as it can only be observed at the chromatid level. CO-FISH, or strand-specific fluorescence "in situ" hybridization, facilitates strand-specific targeting of DNA with fluorescently-tagged probes. It exploits the uniform orientation of major satellites relative to the direction