Normal sequenceThe unchanged DNA, read three bases at a time. Every other strip is compared with it.
SubstitutionOne base is replaced by a different base. The number of bases stays the same.
InsertionOne or more bases are added to the DNA. Here one extra base shifts every later codon.
DeletionOne or more bases are lost from the DNA. Here one lost base shifts every later codon.
What it does to the protein 5
Silent mutationThe new codon codes for the same amino acid. The protein does not change.
Missense mutationThe new codon codes for a different amino acid. One amino acid of the protein changes.
Nonsense mutationThe new codon is a stop codon. The protein comes out shortened.
Premature stop codonA stop codon where an amino acid codon used to be. Here TGG became TGA.
Frameshift mutationA base added or lost shifts the reading frame. Every codon after it is read wrongly.
How this list was compiled: Every name checked on 2026-10-01 against the US National Human Genome Research Institute, Talking Glossary (https://www.genome.gov/genetics-glossary/Point-Mutation and the entries Substitution, Missense Mutation, Nonsense Mutation, Frameshift Mutation, Insertion, Deletion, Stop Codon); Wikipedia: Point mutation, Silent mutation, Nonsense mutation, Frameshift mutation, text only; and the University of California Museum of Paleontology, Understanding Evolution: Types of mutations (https://evolution.berkeley.edu/dna-and-mutations/types-of-mutations/). Every codon of the chart checked by script against the NCBI standard genetic code table and Wikipedia, DNA and RNA codon tables. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
A mutation is a change in a DNA sequence. This chart shows one short sequence with the amino acids it codes for, then five mutated copies. The sequence is made up for practice.
Read the full guide
Compare each strip with the top one
DNA is read three bases at a time, and each group of three, a codon, stands for one amino acid. In the first frame one base is swapped for another: a substitution. If the amino acid stays the same, the mutation is silent. If one amino acid changes, it is missense. If the new codon is a stop codon, it is nonsense and the chain ends early. In the second frame a base is added, an insertion, or lost, a deletion. Either one shifts every codon after it: a frameshift.
The letters are the coding strand of the DNA. The messenger RNA reads the same, with U in place of T.
A marked cell is the changed base; a marked box is a changed amino acid.
Questions and answers
What are the types of point mutation?
A point mutation changes a single base pair. A substitution swaps one base for another and can be silent, missense or nonsense. Adding or losing one base is an insertion or a deletion.
What is the difference between a missense and a nonsense mutation?
Both are substitutions. A missense mutation changes a codon to one for a different amino acid, so one amino acid of the protein changes. A nonsense mutation changes it to a stop codon, so the protein is cut short.
What is a frameshift mutation?
An insertion or deletion of a number of bases that is not a multiple of three. Because the code is read in groups of three, every codon after the change is read differently.
Why does a silent mutation not change the protein?
Most amino acids have more than one codon. On this chart TTC becomes TTT, and both code for phenylalanine, so the same amino acid is added.