Genetic diversity arising as a result of mutation

What is a gene mutation?

A change in the DNA base sequence.

When do mutations occur?

Mutations occur spontaneously during DNA replication.

What are the two types of mutattions that can occur during DNA replication?

Base deletion and base substitution.

What is the consequence of a mutation on protein production?

It can lead to the production of a non-functional protein or enzyme.

How can a mutation lead to a non-functional protein or enzyme?

- A mutation will lead to a change in the triplet sequence of DNA

- which will lead to a change in the sequence of codons in mRNA during protein synthesis

- which will change the sequence of amino acids in the primary structure of the polypeptide

- which will change the position of hydrogen, ionic and disulphide bonds in the tertiary structure of protein

- and if the tertiary structure changes then the shape of the protein and therefore the active site of the enzyme will change shape

- which means that the substrate can't bind to the active site and form an enzyme-substrate complex

What is a base deletion mutation?

A mutation where a base pair is removed from the DNA sequence, causing a frameshift.

Why is a base deletion mutation more likely to change the amino acid sequence?

It causes a frameshift that alters the triplet sequence from the point of mutation.

How can base deletion lead to a protein which is non-functional?

The process of base deletion is:

- base pair removed from DNA sequence

which changes triplet sequence from the point of mutation (frameshift)

- this changes the sequence of codons on mRNA after point of mutation

- which leads to a change in sequence of amino acids in the primary structure of the polypeptide

- which changes the position of hydrogen/ionic/ disulphide bonds in tertiary structure of protein

- Which will result in a change in tertiary structure and therefore a protein with a different shape which may be non-functional

What is a base substitution mutation?

A mutation where a base in DNA is replaced with another base.

Why is a base deletion mutation more damaging than substitution?

Not all substitution mutations will result in a change to the amino acid sequence of a protein due to the degeneratre nature of the genetic code

How can base substitution lead to a non-functional protein

- A base (if a base is deleted or substituted then it means that that base and its complementary base have also been deleted or substituted) in DNA replaced with another base

- Which means that there will be a change in the triplet that was effected

- This could lead to a change in one mRNA codon during protein synthesis and therefore one amino acid is different so the sequence of amino acids in primary structure of polypeptide changes

- which changes the position of hydrogen/ionic/ disulphide bonds in tertiary structure of protein

- Which will result in a change in tertiary structure and therefore a protein with a different shape which may be non-functional

How can base substitution not result ina non-functional protein?

due to the degenerate nature of the genetic code, the new triplet may still code for the same amino acid so the sequence of amino acids in the primary structure of the polypeptide remains unchanged

What are mutagenic agents?

Factors that can increase the rate of gene mutation.

Name mutagenic agents

Ultraviolet radiation

Ionising radiation

HPV

Nitrous acid

Tar

What is the potential outcome of a mutation in terms of protein functionality?

It may result in a protein that is non-functional.