Topic 8 - Biology

Define what is meant by a ‘mutation’.

any change in the quantity or structure of DNA of an organism

Define what is meant by a ‘gene mutation’.

any change to the base sequence of the DNA

State the types of gene mutations. [6]

Deletion

Addition

Duplication

Inversion

Translocation

Substitution

Describe what happens during a substitution mutation.

A nucleotide in a section of a DNA molecule is replaced by another nucleotide that has a different base.

Describe what happens during a deletion mutation.

The loss of a nucleotide base from a DNA sequence

Describe what happens during an addition mutation.

The addition of one or more bases inserted into the DNA nucleotide sequence.

Describe what happens during a duplication mutation.

One or more bases are repeated in the base sequence.

Describe what happens during an inversion mutation.

A section of bases become separated from the DNA sequence and rejoin at the same position but in the inverse order.

Describe what happens during a translocation mutation.

A section of bases is moved from one location in the genome to another.

How can the basic mutation rate be increased?

by outside factors known as mutagenic agents

Define what is meant by a ‘mutagenic agent’.

An agent that increases the rate of gene mutations above normal level.

Give examples of mutagenic agents.

Ionising and ultraviolet radiation

Carcinogens

Viruses

What is meant by a ‘carcinogen’?

chemicals that can alter the structure of DNA and interfere with transcription

What can mutations occur in?

Mutations can result in a different amino acid sequence in the encoded polypeptide