3S2+Bio+DNA+Essay+By+Song+Ken+(24)+and+Tan+Yan+You+Eiros+(29)

Task: Write a 300-word essay describing the **components of DNA ** and **how these associate **  with each other to generate the **overall, 3-dimensional structure **  of DNA.
 * __DNA Structure Essay (Biology)__**

Song Ken - **Purple** Eiros Tan - **Blue**

__ Essay __** <span style="color: rgb(153, 0, 255);">Deoxyribonucleic acid (DNA) is a long linear polymer found in the nucleus of a cell, in the shape of a double helix. It is formed from molecules known as nucleotides and each nucleotide consists of a 5-carbon sugar, known as deoxyribose, a nitrogen containing base attached to the sugar, and a phosphate group. The backbone of the double helix structure is formed by the deoxyribose sugar together with the phosphate group whereas the bases are the ones that connect to each other from one side to the other, similar to the rungs of a ladder.

Another characteristic of DNA would be that they are metres long and can be found in all cells of the body. In order to compress itself, it wounds itself around structural proteins known as histones. This is known as a single chromatin thread. As further coils occur for the chromatin thread itself, it eventually forms the structure of an x-shaped chromosome. However, only a particular section of it is ever used for containing the information of how the protein is made. This is known as the gene of the DNA, and each of them is only able to produce a single type of polypeptide.

For a deoxyribose sugar, its own deoxy- prefix sets a difference between its similar counterpart RNA, as the molecule contains one less oxygen atom as compared to a ribose sugar. It is also a pentose sugar, meaning that it consists of 5 carbon atoms. The phosphate group is a collection of phosphate and oxygen atoms, and is bounded to the 5 carbon atom of a deoxyribose sugar by the means of an ester bond. Finally for the nitrogen containing base, two kinds exist: a purine base and a pyrimidine base. From each of the two groups, bases join to the other in order to form a base pair.

<span style="color: rgb(153, 0, 255);">Four different types of nucleotides are found in the DNA, namely Adenine, Guanine, Cytosine and Thymine. They differ only in the nitrogenous base and are given one letter abbreviations, namely A, G, C and T respectively. <span style="color: rgb(153, 0, 255);"> Every Adenine base is joined to a Thymine base by the intermolecular forces of two hydrogen bonding, while a Guanine base is joined to a Cytosine base by three. Therefore, The ratio of A:T and G:C would always be 1:1.

<span style="color: rgb(153, 0, 255);">http://www.blc.arizona.edu/Molecular_Graphics/DNA_Structure/DNA_Tutorial.HTML#Components http://www.johnkyrk.com/DNAanatomy.html http://en.wikipedia.org/wiki/DNA http://wordnetweb.princeton.edu/perl/webwn?s=dna http://en.wikipedia.org/wiki/Nucleotide <span style="color: rgb(153, 0, 255);">
 * __References__**