Define an insertion mutation.

The addition of one or more nucleotides into a DNA sequence.

What is a deletion mutation?

The removal of one or more nucleotides from a DNA sequence.

Why might a single nucleotide substitution have no effect on the protein produced?

It may result in a silent mutation if the new codon still codes for the same amino acid due to the degeneracy of the genetic code.

What is a missense mutation and how does it arise?

A missense mutation occurs when a substitution causes a different amino acid to be incorporated into the polypeptide, potentially altering protein structure and function.

How does a nonsense mutation affect translation?

A substitution creates a premature stop codon, causing early termination of translation and producing a truncated, usually non-functional protein.

OCR A-Level Biology H420

Cell Structure

Topic overview Microscopy, slide preparation and staining Biological drawings, magnification and resolution Eukaryotic cell ultrastructure The secretory pathway and the cytoskeleton Prokaryotic and eukaryotic cells compared

Biological Molecules

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Nucleotides and Nucleic Acids

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Enzymes

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Cell Division, Cell Diversity and Cellular Organisation

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Exchange Surfaces

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Transport in Plants

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Communicable Diseases, Disease Prevention and the Immune System

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Communication and Homeostasis

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Cellular Control

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Patterns of Inheritance

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Cellular Control

Gene mutations and their effects

2 things to know
Components 02 and 03

Overview

Substitution, insertion and deletion, missense and nonsense mutations, why a frameshift is so damaging, and when a mutation is neutral, harmful or beneficial.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Compare substitution, insertion and deletion mutations.

Key term

What is a substitution mutation?

Questions from this subtopic

Each one with the model answer underneath.

1
What is a substitution mutation?
Model answer
The replacement of one or more nucleotides with different nucleotides in a DNA sequence.
2
Define an insertion mutation.
Model answer
The addition of one or more nucleotides into a DNA sequence.
3
What is a deletion mutation?
Model answer
The removal of one or more nucleotides from a DNA sequence.
4
Why might a single nucleotide substitution have no effect on the protein produced?
Model answer
It may result in a silent mutation if the new codon still codes for the same amino acid due to the degeneracy of the genetic code.
5
What is a missense mutation and how does it arise?
Model answer
A missense mutation occurs when a substitution causes a different amino acid to be incorporated into the polypeptide, potentially altering protein structure and function.
6
How does a nonsense mutation affect translation?
Model answer
A substitution creates a premature stop codon, causing early termination of translation and producing a truncated, usually non-functional protein.

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