What is meant by the term penetrance?
Reveal answer
Proportion of people with a genotype who show an associated phenotype in stated conditions.
Key words: penetrance
4(b) INHERITANCE · RECALL
4.36B How often a mutation affects the phenotype
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What is meant by the term regulatory sequence?
Reveal answer
DNA controlling timing, location or amount of gene expression.
Key words: regulatory sequence
What is meant by the term conservative substitution?
Reveal answer
Amino-acid replacement with similar chemical properties.
Key words: conservative substitution
What is meant by the term compensation?
Reveal answer
Reduction of an effect by another allele, gene or pathway.
Key words: compensation
Why mutation effects differ: for Coding consequence, give the lower likely impact and the higher likely impact.
Reveal answer
Lower likely impact: Synonymous change. Higher likely impact: Frameshift/early stop.
Key words: Coding consequence
Why mutation effects differ: for Protein position, give the lower likely impact and the higher likely impact.
Reveal answer
Lower likely impact: Tolerant surface residue. Higher likely impact: Active/binding site.
Key words: Protein position
Why mutation effects differ: for Gene expression, give the lower likely impact and the higher likely impact.
Reveal answer
Lower likely impact: Gene not expressed in tissue. Higher likely impact: Critical developmental expression.
Key words: Gene expression
Why mutation effects differ: for Redundancy, give the lower likely impact and the higher likely impact.
Reveal answer
Lower likely impact: Compensating pathway. Higher likely impact: Unique essential product.
Key words: Redundancy
Why mutation effects differ: for Environment, give the lower likely impact and the higher likely impact.
Reveal answer
Lower likely impact: Condition not challenging pathway. Higher likely impact: Condition exposes requirement.
Key words: Environment
True or false, and why? “A larger DNA change is always more severe.”
Reveal answer
False. Position, gene function and compensation also matter.
True or false, and why? “No phenotype means no biological effect.”
Reveal answer
False. Effects can be subtle, conditional or undetected.
True or false, and why? “One genotype always produces one fixed phenotype.”
Reveal answer
False. Expression, other genes and environment modify outcomes.
Do most mutations have an effect on the phenotype?
Reveal answer
No: most have no effect; some are harmful and a few are beneficial.
Key words: No
Why can a mutation be beneficial?
Reveal answer
New allele gives an advantage → organism more likely to survive and reproduce → passes the allele on.
Key words: survive
Name a mutation effect that can be beneficial to bacteria.
Reveal answer
Antibiotic resistance.
Key words: antibiotic