DNA Supercoiling

The entirety of the genome is very large, and it is hard to imagine the possibility that it even fits inside of a cell, let alone the nucleus of eukaryotes. This ability to condense itself is the result of multiple folding techniques along the strand of DNA and an eventual folding around histone proteins. One such technique is supercoiling, which is the over or under winding of the DNA in a particular area. Supercoiling allows access and therefore expression to those areas on a strand. The over-winding leaves the area of genetic information untouchable by proteins, so it is unable to serve as any active template. Under-winding allows for access and is what allows for expression when it is needed. When it is over-wound the DNA is condensed and therefore takes up less space and is the preferred state when inactive. Enzymes known as topoisomerases are able to change DNA spooling and aid in DNA processes such as transcription and replication. Although useful in compacting DNA, supercoils put strain on the DNA that either must be relieved or accounted for elsewhere in the strand.