Describe the structure of DNA and its importance.

DNA stands for deoxyribose nucleic acid, and essentially carries the genetic instructions for functioning, development, and reproduction. It is stored in the nucleus, within chromosomes which are thread-like structures. DNA is made up of molecules called 'mononucleotides', and each and every one of these molecules have 3 parts to its structure: A 5-carbon sugar (pentose), a nitrogenous base, and a phosphoric acid. When adjacent mononucleotides combine, a phosphodiester bond is created via a condensation reaction eliminating one molecule of water. (This is created as the -OH group on the phosphoric acid of the first mononucleotide reacts with a -H atom on the pentose sugar of another mononucleotide). As many mononucleotides join up, a polynucleotide chain is formed with phosphodiester bonds between the individual mononucleotides. As a result, the structure of DNA can be simplified into a sugar-phosphate backbone, with nitrogenous bases 'hanging' off this. There are 4 possible nitrogenous bases that could be in a molecule of DNA, and these are: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). DNA have 2 polynucleotide chains (twisted around each other into a double helix) which are antiparallel to each other so that the bases from each strand are facing each other, and 'complementary bases' form hydrogen bonds between them. For example, Adenine base is complementary with Thymine base (A-T), and Cytosine is complementary with Guanine (C-G). In one complete twist of the helix, there are 10 complementary base pairs. A gene is a segment of DNA which is located on a chromosome inside the nucleus of a cell, and codes for a molecule with a certain function. Within a gene, there are codons (genetic code) which are are 3 consecutive nitrogenous bases, coding for 1 amino acid. For example, if there were 3 adenine bases (AAA) next to each other on one DNA strand, this codon would code for an amino acid called 'lysine'. So essentially, in a long chain of bases, there would be many codons. These codons would create a sequence of amino acids, which essentially create a protein. Proteins are essential for metabolism, growth and function of a living organism, and therefore DNA is vital to us.