Mutagenesis

Question 1

All mutations can be grouped under?

Answer 1

Base substitution
Insertion
Deletion
Re arrangement

Question 2

Two types of point mutations

Answer 2

Transition = purine to purine or pyrimidines to pyrimidines 
Transversion = purine --> pyrimidines or vice versa

Question 3

Point mutations in the coding region can be …

Answer 3

Silent
Miss sense
Non sense

Question 4

Point mutations in the non coding region can be detrimental as they can change…..

Answer 4

Protein binding sites
Promoter sequences
Splice sites
Gene expression

Question 5

When does frames shift occur?

Answer 5

Addition or deletion of base pairs not in multiple of 3

Question 6

What is the wild type allele?

Answer 6

The allele that is most common within a population and is so considered to be the normal allele

Question 7

Spontaneous mutations could be caused by…..

Answer 7

Errors in DNA replication
DNA bases chemical instability
NOT caused by exposure to known mutagen

Question 8

2 types of spontaneous mutations….

Answer 8

Tautomeric shift - undergone by the 4 bases, proton briefly changes position which causes G to pair with T and A with C
Slippage- occurs during replication. Newly synthesised strand slips out = 1 extra nucleotide on new strand. Template strand loops out = 1 omission of 1 nucleotide on new strand

Question 9

Examples of chemicals / radiations that cause mutations

Answer 9

Alkylating agents - remove a base
Acridine agents - remove or add a base
X rays - break chromosome / delete a few nucleotides 
UV radiation - create thymine dimer
EMS or nitrous acid

Question 10

2 types of DNA repair

Answer 10

Mismatch repair

Excision repair

Question 11

Describe mismatch repair

Answer 11

Enzyme detects nucleotides that don’t base pair in newly replicated DNA.
Incorrect base pair is excised and replaced

Question 12

2 types of excision repair and describe them

Answer 12

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

1) nucleotide excision- repair replaces up to 30 bases and is used I the repair of uv damage and some carcinogens
2) base excision repair - replaces 1–>5 bases and repairs oxidative damage

Question 13

Protein that causes apoptosis when DNA damage is too severe

Answer 13

P53

Question 14

Describe the formation of a tumour

Answer 14

Activated by carcinogens. Derived from individual abnormal cells and generated by a multistep process. Arise from lack of normal growth. All cells same and behaviour depends of cell type.

Question 15

What are oncogenes?

Answer 15

Genes involved in control of cell division
Present in normal cells (normally as proto oncogenes)
Many different classes. May stimulate or inhibit growth

Question 16

What are tumour suppressor genes?

Answer 16

Genes involved in protecting the cell against 1 step in the pathway to cancer

Question 17

Different genetic tests

Answer 17

SDS page  with western blotting
PCR with northern/southern blotting
FISH
Karyotyping
Array comparative genomic hybridisation