L13: Genetic Mutations

E. Goodman

Mutation

Definition: a change that occurs in our DNA sequences.

Mutation Causes

Mistakes are made when DNA is being copied through DNA replication. Results of exposure to environmental factors like UV light, cigarette smoke, and radiation.

Cell Repair

Cells can sometimes repair the error or possible damage before it becomes a fixed mutation (permanent).

Mutation Dis/Advantages

Advantages: Some can have a positive effect → genetic variation

Disadvantages: Some disrupt normal activity that can cause diseases like cancer. Environmental factors introduce radicals that attack DNA, causing these diseases.

Types of Mutations

Genes and Chromosomal Mutations

Point Mutation

Affect a single point in DNA, and one base is substituted for another.
Includes

• Missense

• Silent

• Nonsense

Missense

The substitution changes the amino acid. Essentially it changes it to not make sense. Creates an abnormal protein.
A type of point mutation.

Silent

The substitution does not change the amino acid. Change will occur, however, you won’t even know it’s there. Codons translate to the same product.

Nonsense

The amino acid is changed to a “stop” codon. “Does not make sense to stop the code right in the middle.” A lot of the times when the protein isn’t made.

Frameshift Mutations

The “reading frame” changes, which changes the amino acid sequence.
Includes:

• Deletion

• Insertion

Creates a domino effect, possibly producing a malfunctioning protein.

Deletion

A base is lost (-).

Insertion

An extra base is added (+).