The Genetic Code

Proteins are made by joining amino acids into long chains called polypeptides Each polypeptide contains a cccnbinatias classy or all of the 20 different amino acids. The properties of proteins are detenoined by the order in which different amino acids are janed together to produce polypeptides. How you might wondes can a particular order ci nitrogenous bases in DNA arid RNA molecules he translated into a particular order of amino acids in a polypeptide? The language of mRNA instructions is called the genetic code. As you know RNA contains four different bases: A, U. C. and C. In effect, the code is written ins language that has only four ‘letters How can a code with just four letters cany instructions for 20 different amino acids? The genetic code is reed three letters at a time, so that each “wcrd of the coded message ia three bases long. Each three-letter “w,rt in mRNA is known as a codccs. A coders consists of three  consecutive nudeotides that specify a single amino acid that is to be added to the polypept ide. For example, consider the following RNA sequence:
                       UCGCACGGU
This sequence would be read three bases at a time as:
                       UCG.CAC-GGU
The codons represent the different amino acids:
                       UCG.CAC-GGU
                  Serine-Hlatidine-Glycine

Genetic Code