4.3 MUTATIONS

WHAT IS A MUTATION?

WHAT DO THEY PRODUCE?

WHEN DO THEY OCCUR?

HOW FREQUENT ARE THEY?

Causes a change in the number/sequence of bases in an organism’s DNA.

Produces a change in characteristics which can be [assed onto cells.

Occurs during DNA replication.

Mutations occur with a predictable frequency that varies by species.

HOW CAN THE BASIC MUTATION RATE BE INCREASED?

Outside factors such as mutagenic agents.

Such as:

1. UV.

2. High ionising radiation - can disrupt the structure of DNA.

3. Chemicals.

MUTEGENIC AGENT?

(A factor that) increases (the rate of) mutations.

APART FROM MUTATIONS, EXPLAIN ONE OTHER WAY GENETIC VARIATION IS INCREASED WITHIN A SPECIES?

• Random fusion of gametes.

• Produces new allele combinations/ new maternal and paternal chromosome chominations.

WHAT IS A GENE?

WHERE ARE THEY?

A section of DNA that codes for one polypeptide or functional RNA.

They occupy a fixed position on a CHROMOSOME called a locus.

GAMETIC?

• In sex cells.

• Inherited.

SOMATIC?

• In body cells.

• Accquired.

WHAT ARE THE TYPES OF MUTATION?

(PAPER ONE)

1. Additon/Deletion.

2. Substitution.

WHAT IS AN ADDITION/DELETION MUTATION?

WHAT DOES THIS CHANGE?

WHAT IS THE FANCY NAME?

• Extra base added/removed.

• Changes all subsequent triplets after the mutation, creating a completely new a.a sequence.

• Called a frameshift mutation.

HOW MANY EFFECTS CAN A SUBSTITUTION HAVE?

WHAT ARE THEY?

EXPLAIN THEM?

1. Missense - can cause an a.a in a polypeptide to change, may no longer function properly.

2. Nonsence - change creates a stop codon, marking the end of translation —> production of polypeptide stopped prematurely, altered 3* structure —> non-functional.

3. Degenerate - same a.a coded for due to degenerate nature of genetic code.

WHEN CAN MUTATION BE POSITIVE?

Evolution.

Results in change in polypeptide that changes properties of the protein.

May result in increased reproductive success.

WHEN CAN MUTATIONS HAVE NO EFFECT?

Intron.

Changes a.a but not 3* structure.