DNA compaction
From ResearchID.org, a nexus for researching Intelligent Design
The structure of the DNA within the cell, as explained by most textbooks, is a caricature of its actual compaction and structure. In a eukaryotic cell, the DNA undergoes many levels of twisting, folding, rolling, twirling, and coiling. Given the dense and complex compaction DNA undergoes, only providing a summary in a textbook is understandable.
Here is a brief sketch: DNA forms a double-helix that is wrapped around a histone that is bundled into a nucleosome which makes chains of a nucleosomal array which is held together by linker histones to form chromatin fibers and the chromatin scaffolding that takes its shape with the help of the nuclear matrix which allows chromatin scaffolding loops to become a supercoil that makes up a chromosome which is the genetic material that is in the nucleolus which in turn is in the nucleus which is in a cell.
Let's unpack this system with some of the detail it deserves.
DNADeoxyribonucleic Acid (DNA) --- source Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. DNA is a long polymer of nucleotides and encodes the sequence of the amino acid residues in proteins using the genetic code, a triplet code of nucleotides. DNA is often referred to as the molecule of heredity as it is responsible for the genetic propagation of most inherited traits. Each strand of DNA is a chain of chemical "building blocks", called nucleotides, of which there are four types: adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). | |
Double-helixDouble-helix structure of DNA --- source The DNA double helix typically consists geometrically of two congruent helices with the same axis, differing by a translation along the axis. | |
Histone | |
NucleosomeNucleosomes are made from histones --- source Nucleosome core particle --- source | |
Nucleosomal arrayNucleosomal array --- source Condensed nucleosomes | |
Linker histonesImage:Linker histones.gif Linker histones | |
ChromatinChromatin fibers --- source | |
Chromatin scaffoldingImage:Chromatin scaffolding.jpg Chromatin scaffolding | |
Nuclear matrixNuclear matrix --- source | |
Chromatin scaffolding loopsChromatin scaffolding loop --- source | |
SupercoilImage:Supercoil.jpg Supercoil | |
ChromosomeA chromosome --- source | |
Genetic materialImage:Genetic material.jpg Genetic material | |
NucleolusImage:Nucleolus.jpg Nucleolus | |
NucleusNucleus --- source | |
CellEukaryotic Cell --- source |
