Missense Mutation — Definition & Examples

What's a Missense Mutation?

This type of mutation results in an incorrect amino acid being coded for. It is a substitution point mutation, so a single base is switched with a different, incorrect base. The point mutation leads to a single amino acid changing. This can impact the protein's function.

An easy way to remember this type of mutation is that "missense" looks like "misspelled". A missense mutation is basically a misspelled codon. Because this mutation only switches one nucleotide for another, it will not cause the codon reading frame to shift like it does in a frameshift mutation.

Sickle cell anemia is caused by a missense. A single incorrect amino acid for a protein completely alters how that protein functions. This causes blood cells to be misshapen.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Mutation}}$ : A change in genetic code

$\color{#8925AE}{\text{Point Mutation}}$ : A mutation that occurs at a single point in the DNA sequence

$\color{#8925AE}{\text{Codon}}$ : A group of three nucleobases that codes for a specific amino acid

$\color{#8925AE}{\text{Missense}}$ : A substitution mutation that codes for an incorrect nucleobase

Coding for the Wrong Amino Acid

A missense mutation is a type of point mutation. It results in base pairs which code for an incorrect amino acid. A single amino acid substitution could greatly alter the function of the resulting protein.

How Does It Happen?

Ribosomes read the nucleotide sequence on the mRNA strand in groups of three nucleotides called codons. These codons determine what amino acid is to be placed in the polypeptide chain. A missense happens when a single base pair substitution changes the amino acid that a codon corresponds to.

This could be incredibly dangerous to a protein if a stop codon is accidentally made. A stop codon signals the end of translation, so if one is created early, the resulting protein might not function at all.

(Video) A Comparison of Silent, Missense, & Nonsense Mutations

by Catalyst University