Splice site mutation vs Frameshift mutation
How to tell Splice site mutation and Frameshift mutation apart when a board question makes them look alike.
Splice site mutation breaks RNA processing; frameshift mutation breaks codon grouping in the coding sequence.
Side by side
Splice site mutation disrupts intron removal or exon joining, causing exon skipping, intron retention, cryptic splice use, or abnormal mRNA processing.
Frameshift mutation changes the reading frame through an insertion or deletion not divisible by three, altering downstream codons.
Mutation at consensus donor or acceptor splice sequences prevents normal spliceosome recognition.
Indel length changes codon triplet grouping during translation of the coding region.
Abnormally large/small mRNA, intron retention, exon skipping, or splice donor/acceptor mutation supports splice-site disease.
Coding-region one- or two-base indel with downstream amino acid changes supports frameshift.
The trap
Both can produce abnormal protein, but one is an mRNA processing defect and the other is a reading-frame defect.
The repair move
For mutation mechanism, decide whether the primary defect is splicing the transcript or reading codon triplets.
Try a free question
CoreA patient has a single nucleotide change at the conserved GT at the 5' end of an intron in the dystrophin gene. Analysis of mRNA shows that the intron is no longer removed and is retained in the mature mRNA, with a premature stop codon appearing soon after. Which type of mutation is this?
Show answer and explanation
Answer: A. Splice site mutation. Splice site mutations disrupt the conserved 5' donor (GT) or 3' acceptor (AG) splice site sequences, causing intron retention, exon skipping, or use of cryptic splice sites. The resulting altered mRNA often introduces premature stop codons and severe protein truncation. Beta-thalassemia, neurofibromatosis, and many other disorders can have splice site mutations.
Why the other choices are tempting
- B. Frameshift mutation is an indel in coding sequence, not a single substitution at a splice site.
- C. Missense mutation in coding sequence changes an amino acid; the question describes a splice site, not a coding substitution.
- D. Nonsense mutation in coding sequence creates a stop codon in the open reading frame, not at an intron-exon boundary.
- E. Silent mutation in coding sequence does not change protein; the question describes a splice-altering change.
Flashcards
Tap a card to flip it.
What clue supports Splice site mutation?
Choose Splice site mutation when the stem gives this pattern: Splice site mutation disrupts intron removal or exon joining, causing exon skipping, intron retention, cryptic splice use, or abnormal mRNA processing.
What clue supports Frameshift mutation?
Choose Frameshift mutation when the stem gives this contrasting pattern: Frameshift mutation changes the reading frame through an insertion or deletion not divisible by three, altering downstream codons.
Quick answers
What is the fastest way to tell Splice site mutation from Frameshift mutation?
Splice site mutation breaks RNA processing; frameshift mutation breaks codon grouping in the coding sequence.
What is the key clue for Splice site mutation?
Splice site mutation disrupts intron removal or exon joining, causing exon skipping, intron retention, cryptic splice use, or abnormal mRNA processing.
What is the key clue for Frameshift mutation?
Frameshift mutation changes the reading frame through an insertion or deletion not divisible by three, altering downstream codons.
What is the common trap with Splice site mutation vs Frameshift mutation?
Both can produce abnormal protein, but one is an mRNA processing defect and the other is a reading-frame defect.