A change in a codon from AGC to AGA represents which of the following types of mutation?
This is neither a deletion or an insertion it is just a point mutation. This point mutation does not result in a stop codon (TAA, TAG, or TGA) and so it is a missense mutation.
You might ask could this be a silent mutation? Well the mutation here results in a new amino acid (AGC = serine, AGA = arginine) so the answer is no. Don't try and remember all the amino acid sequences just be aware of the stop codons.
Mutations
A mutation is an alteration in the DNA of a cell. There are several terms you need to be aware of.
| Mutation | Description |
|---|---|
| Missense mutation | With a missense mutation, the new nucleotide alters the codon so as to produce an altered amino acid in the protein product |
| Nonsense mutations | With a nonsense mutation, the new nucleotide changes a codon that specified an amino acid to one of the STOP codons (TAA, TAG, or TGA). Therefore, translation of the messenger RNA transcribed from this mutant gene will stop prematurely. The earlier in the gene that this occurs, the more truncated the protein product and the more likely that it will be unable to function |
| Point Mutation | A point mutation is a simple change in one base of the gene sequence |
| Frame-shift mutation | An insertion or deletion of a number of nucleotides that shifts the sequence resulting in a completely different translation than the original |
| Silent mutation | A mutation that codes for that same amino acid |
