Mutations Lesson

A mutation describes a change in the sequence of nucleotides (letters) in a segment of DNA. 

This can occur due to errors in DNA replication, cell division, or exposure to certain environmental agents.

• Harmful - Causes an enzyme or protein to not function properly

• Helpful - Causes a genetic change that is good for the individual/species

• Neutral (not good or bad) - Doesn't do anything

A substitution mutation describes a change in the nucleotide sequence in which one nucleotide is replaced by another. 

This is the most common type of mutation and is also known as a point mutation.


Point mutations may or may not have an effect on the amino acid sequence

Substitution Mutations

Insertion Mutation

An insertion mutation describes a change in the nucleotide sequence in which one or more additional nucleotides are inserted into the sequence. 

This will change the amino acid sequence in protein synthesis.

A deletion mutation describes a change in the nucleotide sequence in which one or more nucleotides are omitted from the sequence. 

This will change the amino acid sequence in protein synthesis.

​Deletion Mutation

Insertion and deletion mutations are also referred to as frameshift mutations. 

Remember that in protein synthesis the mRNA is read one codon at a time so the nucleotides must be looked at in sets of 3.
 

When a nucleotide is added or removed, the reading frame shifts, resulting in multiple changes to the amino acid sequence following the site of the mutation.

Frameshift Mutation