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A single DNA strip in human cells consists of around 3 billion base pairs and is approximately 2 meters long. Both chains of that length need to be reduced in size to dimensions invisible to the eye. Similarly to the way in which a long thread is wound around a reel, the DNA is packaged and installed in the nucleus through a similar cellular mechanism. The DNA strip is packaged by being wound around nucleosomes, which give rise to chromosomes. The job of the nucleosomes is undertaken by proteins known as histones.
There is a 15-turn section of the DNA spiral in one nucleosome; and this is the length of 150 nucleotides.22 This 15-turn section is wound twice around a protein nucleus, made up of eight histones containing a large number of positively charged amino acids. These perfectly complement the negatively charged phosphates on the DNA. When information written anywhere on the DNA is needed for protein production, the nucleosome opens and the DNA strip is released for "reading." After this, the DNA winds back around the histones, protected from the damaging effects of the molecules around it, until the next time need arises. Genetic data require not just content, but also a sensitive order in their structure and in the features of the surrounding environment.
This order is just one of the works of our Almighty Lord, Creator of the Earth and sky. In one verse, we are told that:
... My Lord is kind to anyone He wills. He is indeed All-Knowing and All-Wise. (Surah Yusuf, 100)
References
- David S. Goodsell, Our Molecular Nature, Springer-Verlag, New York, 1996, p. 39. ↩