CGE: Mutations COPY

Question 1

Mutations

Answer 1

Any change to the base (nucleotide sequence) of DNA.

Question 2

How can the rate of mutations be increased?

Answer 2

By mutagenic agents.

Question 3

Substitution

Answer 3

One or more bases are swapped for another.

Question 4

Deletion

Answer 4

One or more bases are removed.

Question 5

Addition

Answer 5

One or more bases are added.

Question 6

Duplication

Answer 6

One or more bases are repeated.

Question 7

Inversion

Answer 7

A sequence of bases is reversed.

Question 8

Translocation

Answer 8

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 9

The order of DNA bases in a gene determines what? If a mutation were to occur in this gene what might happen?

Answer 9

Determines the sequence of amino acids in a particular polypeptide. If a mutation occurs, the sequence of amino acids in the polypeptide that gene codes for could change.

Question 10

What do polypeptides make up?

Answer 10

Proteins

Question 11

What might a change in amino acid sequence of a polypeptide cause?

Answer 11

A change in the final 3D shape of the protein, which could mean it can’t function properly.

Question 12

Healthwise, what can mutations cause?

Answer 12

Genetic disorders - eg. cystic fibrosis. Increased likelihood of developing certain cancers.

Question 13

Genetic disorders

Answer 13

Inherited disorders caused by abnormal genes or chromosomes. Eg. cystic fibrosis.

Question 14

Give an example of a mutation that might lead to an increased risk of developing cancer.

Answer 14

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

Question 15

Hereditary mutations

Answer 15

When a gamete containing a mutation for a genetic disorder or type of cancer is fertilised - will be present in fetus formed.

Question 16

Are all hereditary mutations harmful?

Answer 16

No - some are beneficial and drive evolution.

Question 17

Silent mutation

Answer 17

Mutation that doesn’t change the order of amino acids.

Question 18

The degenerate nature of the genetic code means what for amino acids? What does this mean for mutations?

Answer 18

Some amino acids are coded for by more than one DNA triplet, eg. tyrosine = TAT/TAC Means that not all mutations will result in a change to the amino acid sequence of the polypeptide.

Question 19

What types of mutations often don’t result in a change in amino acid order?

Answer 19

Substitutions. Inversions.

Question 20

What types of mutations nearly always change the amino acid sequence?

Answer 20

Additions, duplications and deletions.

Question 21

Why do additions, duplications and deletions nearly always change the amino acid sequence?

Answer 21

• Mutations change the number of bases in DNA code.
• Causes a frameshift in the base triplets that follow.
• Triplet code is read in a different way.

Question 22

The base triplets that follow on from the mutation are said to be what?

Answer 22

‘Downstream’ of the mutation.

Question 23

Give examples of mutagenic agents?

Answer 23

Ultraviolet radiation, ionising radiation, some chemicals and some viruses.

Question 24

How can mutagenic agents increase the rate of mutations?

Answer 24

1. Acting as a base - chemicals called base analogs can substitute for a base in DNA replicaiton, changing base sequence.
2. Alter bases - some chemicals can delete or alter bases.
3. Change the structure of DNA - some types of radiation can change the structure of DNA, causing problems in DNA replication.

Question 25

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

Answer 25

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

Eg. 5-bromouracil can substitute for thymine. Can pair with guanine instead of adenine causing a substitution mutation.

Question 26

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

Answer 26

Some chemicals can delete or alter bases.

Eg. alkylating agents can add an alkyl group to guanine, which changes the structure so that it pairs with thymine instead of cytosine.

Question 27

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

Answer 27

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

Eg. UV radiation can cause adjacent thymine bases to pair together.