Glossary

Missense mutation: A mutation that changes an amino acid in a protein. Also called a nonsynonymous mutation.

Nonsense mutation: A mutation that changes an amino acid in a protein to a stop codon which ends synthesis of the protein at that location. These mutations shorten the length of the protein.

Substitution mutation:  This is when a nucleotide in the gene sequence is replaced by another nucleotide.  We refer to the nucleotides as A, C, G, and T (for adenosine, cytosine, guanine, and thymidine). 

Insertion mutation: This occurs when extra nucleotides are inserted into a place in the DNA in the gene.

Deletion mutation: This occurs when nucleotides are lost, or deleted from the DNA in the gene.

Frameshift mutation:  The genetic code is a series of three nucleotides in a row that tell the cell which amino acid to put into the protein at that location.  Insertion and deletion mutations can change the “reading frame” of the genetic code.  For example, by analogy, this sentence:  “Bob ran  one lap”.  If one of the letters is removed, “ie the second b” and the letters are still parsed in groups of three (as the genetic code does),  it will read “ Bor  ano nel  ap.”  And thus, the frameshift mutation  changes the meaning of the code.

Genetic Code:  A series of three DNA nucleotides (referred to as A, C, G, and T) that is read by the cellular machinery to make a sequence of amino acids that become a protein.  Proteins are also known as enzymes, receptors, and transporters to name some examples.  The GRIN, GRIA, GRIK, and GRID genes encode receptor proteins that respond to the neurotransmitter L-glutamate.