MUTAGENS AND GENE EXPRESSION

Question 1

What is the definition of a mutation?

Answer 1

Any change to the base (nucleotide) sequence of DNA

Question 2

How can mutations be caused?

Answer 2

Errors during DNA replication

Question 3

How can mutations be increased?

Answer 3

By the presence of mutagenic agents

Question 4

What are the types of mutations that can occur?

Answer 4

1. Substitution
2. Deletion
3. Addition
4. Duplication
5. Inversion
6. Translocation

Question 5

What happens when a substitution mutation occurs?

Answer 5

One or more bases are swapped for another

Question 6

What happens when a deletion mutation occurs?

Answer 6

One or more bases are removed

Question 7

What happens when an addition mutation occurs?

Answer 7

One or more bases are added

Question 8

What happens when a duplication mutation occurs?

Answer 8

One or more bases are repeated

Question 9

What happens when an inversion mutation occurs?

Answer 9

A sequence of bases is reversed

Question 10

What happens when a translocation mutation occurs?

Answer 10

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

Question 11

What mutation is presented below? Highlight what has changed:

ATGCCT → ATTCCT

Answer 11

Substitution mutation:

ATGCCT → ATTCCT

Question 12

What mutation is presented below? Highlight what has changed:

ATGCCT → ATCCT

Answer 12

Deletion mutation:

ATGCCT → AT(G)CCT (G is removed)

Question 13

What mutation is presented below? Highlight what has changed:

ATGCCT → ATGACCT

Answer 13

Addition mutation:

ATGCCT → ATGACCT (A is added)

Question 14

What mutation is presented below? Highlight what has changed:

ATGCCT → ATGCCCCT

Answer 14

Duplication mutation:

ATGCCT → ATGCCCCT (CC is repeated)

Question 15

What mutation is presented below? Highlight what has changed:

ATGCCT → ATCCGT

Answer 15

Inversion:

ATGCCT → ATCCGTT (GCC is reversed to CCG)

Question 16

What does the order of DNA bases in a gene determine?

Answer 16

The sequence of amino acids in a particular polypeptide

Question 17

If a mutation occurs in a gene, what could change?

Answer 17

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

Question 18

What do polypeptides make up?

Answer 18

Proteins

Question 19

How does a change in the amino acid sequence of a polypeptide affect a protein?

Answer 19

It may change the tertiary structure of the protein, which could mean it won’t work properly

Question 20

How can a mutation in a polypeptide that makes up an enzyme limit the production of enzyme-substrate complexes?

Answer 20

1. The mutation may effect: base sequence → amino acid sequence → polypeptide chain → tertiary structure → active site
2. The active site will no longer be complimentary, and limited E-S complexes will form

Question 21

What is an example of a mutation increasing the likelihood of developing certain cancers?

Answer 21

Mutations on the gene BRCA1 can increase the chances of developing breast cancer

Question 22

What are genetic disorders?

Answer 22

Inherited disorders caused by abnormal genes or chromosomes

Question 23

What’s an example of a genetic disorder?

Answer 23

Cystic fibrosis

Question 24

Explain how a hereditary mutation can occur:

Answer 24

If a gamete (sex cell) containing a mutation for a type of cancer/genetic disorders caused is fertilised, the mutation will be present in the foetus formed.

Question 25

What is a hereditary mutation?

Answer 25

When a cancer or genetic disorder is passed on to offspring

Question 26

Why do not all mutations affect the order of amino acids in a protein?

Answer 26

1. Genetic code is degenerate, meaning that some amino acids are coded for by more than one DNA triplet
2. This means that not all types of mutation will result in a change to the amino acids sequence of the polypeptide

Question 27

What mutations will almost always change the amino acid sequence of a polypeptide, and why?

Answer 27

1. Addition, duplication and deletion
2. They all change the number of bases in the DNA code
3. This causes a frame-shift in the base triplets that follow.