What is meant by the term silent mutation?
Reveal answer
DNA change that does not change the amino-acid sequence in the stated context.
Key words: silent mutation
4(b) INHERITANCE · RECALL
4.35B A DNA change and the phenotype
15 recall questions · Biology only (B): not in Science (Double Award). Answer from memory, reveal the answer, then rate yourself. Ratings stay on this device.
Ratings are saved in this browser on this device, under a KS4 key kept separate from International A Level recall. Written answers are temporary and cleared when you leave the page. Use Reset to clear the ratings on this device.
What is meant by the term missense mutation?
Reveal answer
DNA change causing one amino-acid substitution.
Key words: missense mutation
What is meant by the term nonsense mutation?
Reveal answer
DNA change creating a stop codon.
Key words: nonsense mutation
What is meant by the term frameshift?
Reveal answer
Change in codon reading frame after insertion/deletion not divisible by three.
Key words: frameshift
Possible mutation outcomes: for Synonymous substitution, give the protein effect and the possible phenotype.
Reveal answer
Protein effect: Same amino acid. Possible phenotype: Often no detectable effect.
Key words: Synonymous substitution
Possible mutation outcomes: for Missense substitution, give the protein effect and the possible phenotype.
Reveal answer
Protein effect: Different amino acid. Possible phenotype: Variable effect.
Key words: Missense substitution
Possible mutation outcomes: for Nonsense substitution, give the protein effect and the possible phenotype.
Reveal answer
Protein effect: Early stop. Possible phenotype: Often shortened protein.
Key words: Nonsense substitution
Possible mutation outcomes: for Frameshift, give the protein effect and the possible phenotype.
Reveal answer
Protein effect: Many downstream amino acids altered. Possible phenotype: Often major effect.
Key words: Frameshift
Possible mutation outcomes: for Regulatory change, give the protein effect and the possible phenotype.
Reveal answer
Protein effect: Expression altered. Possible phenotype: Amount/timing can change.
Key words: Regulatory change
True or false, and why? “Every base change changes an amino acid.”
Reveal answer
False. Code redundancy can make a substitution synonymous.
True or false, and why? “Every amino-acid change causes disease.”
Reveal answer
False. Effect depends on position and protein function.
True or false, and why? “Only coding DNA mutations matter.”
Reveal answer
False. Regulatory DNA changes can alter gene expression.
Suggest why a change of one DNA base may have no effect on the protein made.
Reveal answer
The new triplet may still code for the same amino acid, or the change is in non-coding DNA.
Key words: same amino acid
How can a gene mutation change a protein?
Reveal answer
Base sequence changes → different amino acid sequence → protein folds into a different shape → may not work.
Key words: amino acid
Why can a mutation in an enzyme’s gene stop the enzyme working?
Reveal answer
Different amino acids → active site changes shape → substrate no longer fits.
Key words: active site