Mutations are changes in a cell’s DNA sequence. When a mutation happens in the coding sequence of a gene, the resulting protein is changed. In this lesson, discover what a nonsense mutation is and what effects it has on the protein that is made from a gene.
Nonsense Mutation Definition
When you think about a mutant, you might think about sci-fi movies where mutated creatures become powerful and evil and then attempt to destroy the world.
But what are mutations, really? Mutations are changes to a cell’s DNA sequence, and there are several different types.A nonsense mutation is a point mutation that introduces a premature stop codon into the part of the gene that encodes a protein. A stop codon is like a period at the end of a sentence. It instructs the ribosome to stop making the protein. So, if a mutation leads to an early stop codon, only part of the protein will be made.
Half-baked proteins that result from nonsense mutations are often nonfunctional or defective. Now let’s learn more about how nonsense mutations work and their consequences.
Genetic Code Review
The DNA sequence of the coding region of a gene is transcribed into a messenger RNA molecule, whose sequence is in turn read and decoded by the ribosome and transfers RNAs during translation.The sequence of a messenger RNA is read in groups of three nucleotides called codons.
Each possible combination of the three RNA nucleotides (A, G, C and U) codes for an amino acid, translation start or translation stop. What you’re looking at on screen is a table that shows what each codon means to the ribosome and transfer RNAs.
|Explore There are 64 different codons, and