Frameshift mutation vs Missense, nonsense, and silent mutations
How to tell Frameshift mutation and Missense, nonsense, and silent mutations apart when a board question makes them look alike.
Frameshift changes the downstream reading frame; missense changes one amino acid; nonsense creates stop; silent changes no amino acid.
Side by side
Frameshift mutation results from insertion or deletion not divisible by three, shifting the reading frame and changing downstream amino acids, often causing premature stop.
Missense changes one amino acid, nonsense creates a stop codon, and silent changes a codon without changing the amino acid.
Indels alter codon grouping for every downstream codon after the mutation.
Single-base substitutions usually alter one codon, with effect depending on codon redundancy and whether a stop codon appears.
Insertion/deletion with altered downstream reading frame supports frameshift.
Single amino acid change supports missense; early stop supports nonsense; same amino acid supports silent.
The trap
Not every insertion or deletion is frameshift; multiples of three can preserve the reading frame.
The repair move
For mutation types, ask whether codon grouping changed, whether a stop codon appeared, and whether the amino acid changed.
Try a free question
CoreA patient with Duchenne muscular dystrophy has a single nucleotide DELETION in exon 45 of the dystrophin gene. The downstream amino acid sequence is completely altered, with a premature stop codon appearing 27 codons later, producing a truncated, nonfunctional protein. Which type of mutation is this?
Show answer and explanation
Answer: A. Frameshift mutation. Frameshift mutations result from insertion or deletion of a number of nucleotides NOT divisible by three, shifting the downstream reading frame and altering every codon thereafter, typically producing a premature stop. Duchenne muscular dystrophy frameshift mutations produce truncated dystrophin and severe disease; Becker muscular dystrophy in-frame deletions preserve some dystrophin function.
Why the other choices are tempting
- B. Missense changes one amino acid through a single substitution, not a frame shift.
- C. Nonsense creates a stop codon through a single substitution, not by frame shifting.
- D. Silent does not change the amino acid sequence at all.
- E. Splice site mutation disrupts intron removal, not the coding reading frame directly.
Flashcards
Tap a card to flip it.
What clue supports Frameshift mutation?
Choose Frameshift mutation when the stem gives this pattern: Frameshift mutation results from insertion or deletion not divisible by three, shifting the reading frame and changing downstream amino acids, often causing premature stop.
What clue supports Missense, nonsense, and silent mutations?
Choose Missense, nonsense, and silent mutations when the stem gives this contrasting pattern: Missense changes one amino acid, nonsense creates a stop codon, and silent changes a codon without changing the amino acid.
Quick answers
What is the fastest way to tell Frameshift mutation from Missense, nonsense, and silent mutations?
Frameshift changes the downstream reading frame; missense changes one amino acid; nonsense creates stop; silent changes no amino acid.
What is the key clue for Frameshift mutation?
Frameshift mutation results from insertion or deletion not divisible by three, shifting the reading frame and changing downstream amino acids, often causing premature stop.
What is the key clue for Missense, nonsense, and silent mutations?
Missense changes one amino acid, nonsense creates a stop codon, and silent changes a codon without changing the amino acid.
What is the common trap with Frameshift mutation vs Missense, nonsense, and silent mutations?
Not every insertion or deletion is frameshift; multiples of three can preserve the reading frame.