What are genes?
Genes are pieces of DNA that have been identified and are known to code for a protein. Within a gene each group of three nucleotides forms a codon, so called because it codes for an amino acid. You can see this as a syllable which (if it is in a readable location, i.e. within a gene) contains the information required to form an amino acid. GAA! CTA!
Amino acids are the building blocks of proteins. The sequence of bases in our DNA defines the sequence in which amino acids are joined together. If the sequence of information in the codons is correct, this results in the formation of the correct proteins and therefore allows the cells in our body to function correctly.
Every protein begins with the same amino acid, which corresponds to the 'start codon' ATG. The end of a gene can be indicated by various different 'stop codons'.
Using four different letters you can make 64 different codons - 43 - but there are only 20 different amino acids. Different codons are also synonyms for each other: they code for the same amino acid.