MUTATIONS

What is a mutation?

A change in the DNA sequence of an organism.

How can mutations affect proteins?

They can change the amino acid sequence, which may change the structure and function of the protein.

What is a base substitution mutation?

One DNA base is replaced by another base.

What is a silent mutation?

A base changes, but the same amino acid is still produced, so the protein is usually unchanged.

Why can a silent mutation occur?

More than one codon can code for the same amino acid (degeneracy of the genetic code).

What is a missense mutation?

A base substitution changes a codon, causing a different amino acid to be added.

What is the effect of a missense mutation?

It may change the protein's shape and function.

What is a nonsense mutation?

A mutation changes a codon into a stop codon.

What is the effect of a nonsense mutation?

Protein production stops early, creating a shortened protein that is usually non-functional.

What is an insertion mutation?

One or more bases are added to the DNA sequence.

What is a deletion mutation?

One or more bases are removed from the DNA sequence.

What is a frameshift mutation?

An insertion or deletion changes the reading frame of the genetic code.

Why can a frameshift mutation have a major effect?

It changes all the codons after the mutation, potentially changing many amino acids and the whole protein.

How can a mutation affect phenotype?

→ Mutation changes DNA → may change mRNA codons → may change amino acids → may change protein → may change phenotype

Are all mutations harmful?

No. Mutations can be harmful, beneficial, or have no effect.