Mutagenesis

Question 0

What is a silent mutation

Answer 0

A single base change which doesn’t change the amino acid

Question 1

What is a missense mutation?

Answer 1

One amino acid substituted for another, normally by a single base change

Question 2

What can a silent mutation cause?

Answer 2

It can disrupt RNA splicing and cause inheritable diseases

Question 3

What is a nonsense mutation?

Answer 3

An amino acid codon is mutated to a stop codon

Question 4

What is a frameshift mutation?

Answer 4

The reading frame of mRNA is altered by insertions, deletions, slice-site mutation
Not a multiple of three

Question 5

What is a point mutation?

Answer 5

A base substitution

Question 6

What is a transition point mutation?

Answer 6

When a purine is substituted for a purine. Same with pyrimidines

Question 7

What is a transversion point mutation?

Answer 7

When a purine is changed for a pyrimidine and vice versa

Question 8

How can a spontaneous mutation occur?

Answer 8

Error in DNA replication

DNA bases have slight chemical instability

Question 9

What does the rate of spontaneous mutation depend on for different genes?

Answer 9

The size of the gene

The sequence

Question 10

Give examples of chemicals that cause induced mutations and what change they can cause

Answer 10

Alkylating agents - remove a base
Acridine agents - add/remove a base
X-rays - break chromosomes or delete nucleotides
UV radiation - creates thymidine dimers

Question 11

What is a mutation?

Answer 11

A change in a nucleic acid sequence, which can be the deletion, insertion, or rearrangement of one or many nucleotides.

Question 12

What is a wild type?

Answer 12

An individual within a population displaying a wild type trait, which is the trait that is most common in that population

Question 13

What is tautomeric shift?

Answer 13

When a proton briefly changes position in a base. It behaves as an altered template base during replication.

Question 14

What pairs are joined in tautomeric forms?

Answer 14

C and A

T and G

Question 15

What is mismatch repair?

Answer 15

Enzymes detect nucleotides which don’t base pair in newly replicated DNA.
The incorrect base pair is excised and replaced.

Question 16

What is proof reading?

Answer 16

Detection of mismatched base pairs

Question 17

What is excision repair?

Answer 17

Damaged DNA is removed by excision of bases and replacement is done by DNA polymerase

Question 18

What is the different between nucleotide excision and base excision repair?

Answer 18

Nucleotide repair

• replaces up to 30 bases
• repair of UV damage and some carcinogens

Base repair

• replaces 1-5 bases
• repairs oxidative damage

Question 19

What can tumour cells do? (6 things)

Answer 19

• Cells divide independently of external growth signals
• Ignore external anti-growth signals
• Avoid apoptosis because DNA is damaged so much
• Divide indefinitely without senescence
• Stimulate sustained angiogenesis
• Invade tissue and establish secondary tumours

Question 20

What are oncogenes?

Answer 20

Genes involved in control of cell division. Can inhibit/stimulate growth

Question 21

How can PCR be used in detecting mutations?

Answer 21

If the restriction site for a particular enzyme is destroyed by the mutation, then the mutated gene will have fewer fragments if digested with that enzyme, as it lacks the site.

Question 22

In diagnosing genetic diseases, what is Southern blotting good for?

Answer 22

When there is a need to analyse larger segments in and around the gene and also for triple repeat disorders.

Question 23

What is array-CGH good for?

Answer 23

Screen for sub-microscopic chromosomal deletions for which the locus cannot be determined by the patient’s phenotype.