This is the biological language that ensures that the genetic material, the DNA and RNA is translated into proteins. Our bodies require thousands of proteins to function normally and the information needed to produce them is locked up inside the genetic code.
What is a Genetic Code?
To understand the genetic code we need to get to grips with some basic genetics.
Genes and proteins are both written in different languages. Genes are made of DNA, and proteins are constructed out of amino acids. Now genes make proteins, so the genetic information has to be translated if a cell is to manufacture proteins.
The first step is for DNA to be converted to mRNA (messenger RNA) which happens inside the nucleus. The mRNA then moves outside the nucleus to the ribosomes which is where protein synthesis takes place. Ribosomes move along the mRNA strand and add amino acids in a very specific way.
The ribosomes read the mRNA sequence 3 nucleotides at a time. Then during this process along comes another set of chemicals called tRNA (transfer RNA). Each tRNA carries on one of its ends an amino acid. It binds to a complementary strand on the mRNA and this goes on and on until there are enough amino acids to make a protein and a stop signal halts the protein manufacture.
That's it in a nutshell, or a biological cell - the genetic code; but we should go just a little bit deeper with our explanation.
Codons
Codons are a triplet of nucleotides ('3 nucleotides at a time') on the mRNA. Each codon encodes for one of 20 amino acids. So for example, if your triplet of nucleotides, or codon, looks like this - UUA or UUG, the amino acid is Leucine. In fact the genetic code consists of 64 codons to make all twenty amino acids which in turn make all the proteins we need.
Features of the genetic code:
1) 61 codons code for amino acids and three codons do not code for any amino acids. They function as stop codons.
2) One codon codes for only one amino acid, hence, it is unambiguous and specific.
3) Some amino acids are coded by more than one codon, hence the code is degenerate. Most of this degeneracy involves the third nucleotide of a codon.
4) The codon is read in mRNA in a continuous fashion. There is no punctuation.
5) AUG codon has dual functions. It codes for Methionine (met), and it also act as an initiator codon to start protein synthesis.
The genetic code is universal ....
.... well almost. The same codons are assigned to the same amino acids and there are the same stop and start codons in almost every plant, animal and microorganism.