What Is Point Mutation

Molecule Tutorials - Herong's Tutorial Examples

∟What Is Point Mutation

Provides a quick introduction of point mutation, which is a gene mutation that changes a single nucleotide base pair of DNA or RNA.

What Is Point Mutation? - A point mutation, also called base-pair substitution, is a gene mutation that changes a single nucleotide base pair of DNA or RNA.

Point mutations can be categorized based on the impact on protein expression.

Silent Mutation: Although a change in the DNA sequence occurs, this type of mutation does not change the protein that is to be produced. This is because multiple genetic codons can encode for the same amino acid. Amino acids are coded for by three-nucleotide sets called codons. For example, the amino acid arginine is coded for by several DNA codons including CGT, CGC, CGA, and CGG (A = adenine, T = thymine, G = guanine, and C = cytosine). If the DNA sequence CGC is changed to CGA, the amino acid arginine will still be produced.
Missense Mutation: This type of mutation alters the nucleotide sequence so that different amino acid is produced. This change alters the resulting protein. The change may not have much effect on the protein, may be beneficial to protein function, or may be dangerous. Using our previous example, if the codon for arginine CGC is changed to GGC, the amino acid glycine will be produced instead of arginine.
Nonsense Mutation: This type of mutation alters the nucleotide sequence so that a stop codon is coded in place of amino acid. A stop codon signals the end of the translation process and stops protein production. If this process is ended too soon, the amino acid sequence is cut short and the resulting protein is most always nonfunctional.