DNA

=DNA=

__Structure__
==A **__nucelotide__** is the smallest piece of DNA or RNA. It consists of a phosphate, a sugar and a nitrogen base. In order to build a molecule of DNA or RNA, nucleotides must be linked together over and over (as seen above).==

__Differences between DNA and RNA__
==RNA is a single strand of nucleotides linked together. It has a slightly different sugar than DNA and instead of having the nitrogen base 'T' (stands for Thymine) it uses a nitrogen base 'U' (stands for Uracil). A single RNA usually lasts a few minutes before it breaks down.==

==DNA is double stranded. So two long chains of nucleotides link together by something called a hydrogen bond (in the picture above, these are shown as dotted lines). A single DNA can last many years (sometimes many millions of years) before it breaks down.==

This process results in one DNA molecule becoming two identical DNA molecules.

 * The DNA is unzipped.
 * New nitrogen bases are added using the base-pairing rules.
 * This continues until the whole molecule is copied.
 * Each new DNA is made up of half the old molecule and half new.

__Translation__
==Translation is when an mRNA is read by a molecule known as a ribosome. This ribosome adds a certain amino acid depending on what three letters of mRNA it just read. The amino acids are added one at a time until a long protein is made. The protein can do lots of different things, from being protein that makes up hair, to protein that digests food, or protein that makes the brain function.==

Mutations are random changes in a DNA sequence. They can be caused by radiation, certain chemicals and viruses.
==Many mutations are 'silent', they do not change the protein that is made during translation. Some mutations can actually make a new protein that is different (and may be better), most mutations that are not 'silent' make a not good protein that cannot do its function.==