The blueprint for life is encoded in the DNA (deoxyribonucleic acid) of all animals. DNA is a polymer strain of four different bases of two different types; the purines adenosine (A) and guanine (G) and the pyrimidines thymine (T) and cytosine (C). Every cell in our body, except germline cells, immune cells and erythrocytes, has the same set of DNA. The DNA contains genes that can be transcribed to messenger ribonucleic acid (mRNA) which serves as the template to be translated to protein. Proteins (and RNAs) carry out the biochemical processes in the cell like metabolism, signal transduction and DNA transcription. DNA in the mammalian cell is about two meter long and has to be compressed in a small nucleus that is about 5 micrometre wide. In order to fit all the DNA into this tiny space it is wrapped around proteins called histones. Around 200 base-pairs are wrapped around eight histones which are organised in a structure called a nucleosome creating a “beads on a string” conformation. Although the wrapping of DNA around nucleosomes condenses the DNA about seven times this is not sufficient to explain the compact structure of the genome. Multiple nucleosomes create chromatin that further compacts the DNA and forms the chromatid. Chromatin can be in a closed or an open conformation and switch between these conformations. This is called chromatin remodelling.

F.G. Grosveld (Frank)
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam

van Riel, B.P. (2011, February 23). Runx1 is Required for Erythroid Development. Erasmus University Rotterdam. Retrieved from