Mutations

Question 1

What is a mutation?

Answer 1

A change to the base (nucleotide) sequence of DNA

Question 2

What is a genome?

Answer 2

Entire set of genes/genetic material present in a cell/organism

Question 3

What is a proteome?

Answer 3

Entire complement of proteins that can be expressed from those genes

Question 4

Describe features of a mutation

Answer 4

• natural
• random
• happens continuously (always happening)

Question 5

What are mutations caused by?

Answer 5

Errors during DNA replication

Question 6

What can increase the likelihood of mutations?

Answer 6

Physical and chemical factors that affect DNA
Mutagenic agents

Question 7

Give examples of mutagenic agents

Answer 7

Exposure to ionising radiation
Exposure to carcinogenic chemicals

Question 8

What is a substitution mutation?

Answer 8

When one or more bases are swapped for another.
E.g. ATGCCT becomes ATTCCT

Question 9

What is a deletion mutation?

Answer 9

When one or more bases are removed
E.g. ATGCCT becomes ATCCT

Question 10

What is an insertion/addition mutation?

Answer 10

When one or more bases are added.
E.g. ATGCCT becomes ATGACCT

Question 11

What is a duplication mutation?

Answer 11

When one or more bases are repeated
E.g. ATGCCT becomes ATGCCCCT

Question 12

What is an inversion mutation?

Answer 12

When a sequence of bases is reversed.
E.g. ATGCCT becomes ACCGTT

Question 13

What is a translocation mutation?

Answer 13

When a sequence of bases is moved from one location in the genome to another. This could be movement within the same chromosome or movement to a different chromosome.

Question 14

What happens if a mutation occurs in a gene?

Answer 14

The sequence of amino acids in the polypeptide that it codes for could be changed

Question 15

What may happen as a result of a change in the base sequence?

Answer 15

The primary structure of a protein may change. This will have a knock on effect on the secondary and tertiary structure of the protein?

Question 16

What happens if mutation occurs in a protein that is an enzyme?

Answer 16

It would cause the active site of the enzyme to change shape meaning it could no longer form enzyme substrate complexes.

Question 17

Why don’t all mutations affect the order of amino acids?

Answer 17

The genetic code is degenerate which means that some amino acids are coded for by more than one DNA triplet.
This means not all types of mutations will result in a change to the amino acid sequence of the polypeptide

Question 18

What types of mutations do not affect the order of amino acids?

Answer 18

Substitutions
Inversions

Question 19

What is the name given to the type of mutation that doesn’t cause a change in the amino acid order?

Answer 19

Silent mutation

Question 20

What types of mutations do cause a change in the amino acid order?

Answer 20

Additions
Duplications
Deletions

Question 21

What is the name given to the type of mutation that does cause a change in the amino acid order?

Answer 21

Frameshift mutation

Question 22

Why do frameshift mutations occur?

Answer 22

Some mutations change the number of bases in the DNA code.
This causes a shift in the base triplets that follow so that the triplet codon is read in a different way.

Question 23

What three ways can mutagenic agents increase the rate of mutations?

Answer 23

Acting as a base
Altering bases
Changing the structure of DNA

Question 24

How can mutagenic agents acting as a base increase the rate of mutations?

Answer 24

Chemicals called base analogs can substitute for a base during DNA replication, changing the base sequence in the new DNA.

Question 25

How can mutagenic agents altering bases increase the rate of mutations?

Answer 25

Some chemicals can delete or alter bases, so that bases pair with a different base.

Question 26

How can mutagenic agents changing the structure of DNA increase the rate of mutations?

Answer 26

Some types of radiation can change the structure of DNA which causes problems during DNA replication