Topic 4: Genetic variation - mutations

Question 1

Define genetic mutation.

Answer 1

Change in the base sequence of DNA, occurring randomly during DNA replication.

Question 2

Define mutagenic agent.

Answer 2

A factor that increases the rate of genetic mutations.

Question 3

What are some examples of mutagenic agents?

Answer 3

-UV light
-Chemicals (carcinogens)

Question 4

What are the two types of gene mutations?

Answer 4

Substitution and Deletion

Question 5

What is substitution in genetic mutation?

Answer 5

When a base sequence is swapped for a different base.

Question 6

What is a deletion genetic mutation?

Answer 6

When a base is deleted, causing a frameshift where everything after the point of mutation shifts.

Question 7

Why is the nature of the degenerate code useful?

Answer 7

If a mutation occurs, and changes 1 base in a triplet, the new triplet might still code for the same amino acid.

Question 8

Explain why a mutation can lead to the production of a non-functional enzyme? (6 Marks)

Answer 8

-Changes the sequence of base triplets in DNA
-So changes the sequence of codons on mRNA
-Changes the sequence of amino acids in the polypeptide
-Which changes the position of hydrogen/ionic/disulphide bonds
-Changes protein tertiary structure
-Causes enzymes active site to change shape so the substrate can no longer bind and form enzyme-substrate complexes.