A mutation is any random change in the DNA. The sequence of amino acids is critical to the performance of a protein; even a single amino acid in the wrong place can cause an enzyme to be non-functional or cause a disease such as Sickle Cell Anemia.
For years, the exact means by which the DNA coded for structures, chemicals and other behaviors in living things was a mystery. Scientists now know which mRNA codons match each amino acid. This means that if you know the sequence of DNA or mRNA, you can figure out the sequence of amino acids that make a protein.
The entire protein would actually require a much longer sequence of DNA bases.
Whenever a protein needs to be made, the correct DNA sequence for that protein is copied to a molecule called (mRNA).
This begins with DNA in the nucleus and ends with the final protein in the cytoplasm.
To do this we need to be able to read the genetic code just as tRNA can.