3G2+Bio+Essay+by+Chang+Hui,+Jun+Rong,+Ming+Shen,+Brandon

Brandon - Black Chang Hui - Blue Zhi Rong - Green Ming Shen - Red

DNA stands for deoxyribonucleic acid. It is a molecule that carries genetic information necessary for all cellular functions which include cell division and cell differentiation.

The basic unit of DNA is called a nucleotide. Each nucleotide is made up of a sugar called deoxyribose, a phosphate group and a nitrogen-containing base. There are 4 types of nitrogen-containing bases in DNA - adenine (A), thymine (T), cytosine (C) and guanine (G). These different bases then form different nucleotides with the phosphate group and deoxyribose sugar - adenine nucleotide, thymine nucleotide, cytosine nucleotide and guanine nucleotide. These nucleotides can then join up together by a condensation reaction through a condensation reaction between the phosphate group of on nucleotide and the hydroxyl group on carbon 3 of the sugar of the other nucleotide to form polynucleotides. Phosphodiester bonds link the nucleotides together. Two parallel polynucleotides chains will make up a DNA molecule. The 2 chains run in opposite directions. The bases of one chain are bonded to those of the opposite chain according to the rule of basic pairing. DNA has a sugar-phosphate backbone that consists of a phosphate group and deoxyribose sugar. The nucleotides are just like rungs of a ladder while the sugar-phosphate backbone is like the sides of the ladder.  References: 1. http://www.blc.arizona.edu/Molecular_Graphics/DNA_Structure/DNA_Tutorial.HTML#Components 2.http://www.accessexcellence.org/RC/VL/GG/structure.php