Genetics

Question 1

CYP2A6

Answer 1

Related to metabolism of nicotine

Higher expression related to nicotine addiction

Question 2

CYP2C8

Answer 2

Related to metabolism of Cerivastatin

Question 3

CYP2C9

Answer 3

Related to metabolism of drugs like warfarin, phenytoin
Makes up 20% of hepatic CYP and metabolises 10% of drugs
Inhibited by oral contraceptives

Question 4

CYP2C19

Answer 4

Related to metabolism of antidepressants and PPI’s

Question 5

CYP3A’s

Answer 5

Metabolises 50% of all drugs and endogenous substances
3A4-adult endogenous metabolism
3A7- Embryonic enzyme
3A5- present in both foetus and adult

Question 6

CYP2D6

Answer 6

V important 
Responsible for the metabolism of 25% of all drugs and significantly affects them including:
anti emetics 
anti-cancer
anti-depressants 
neuroleptics 
anti-arrythmics 
analgesics

Question 7

P-gp (P glycoprotein)

Answer 7

Acts as efflux pump stopping xenotoxins/biotics from entering circulation from GI and entering CNS (part of the BBB)

Expression on lumen side results in:
less drug abosrbed from GI
increased excretion into bile/urine
less entry into CNS

Question 8

TPMT -Thiopurine Methyltransferase

Answer 8

Catalyses thiopurine drugs

90% of people are rapid metabolisers
10% intermediate
0.3% are poor metabolisers- these guys are at high risk of toxicity due to accumulation of drug as it isn’t being inactivated

Question 9

Host for insulin production

Answer 9

E.coli
Yeast
For diabetes

Question 10

Host for factor VIII production

Answer 10

Mammalian cells

Used for haemophilia

Question 11

Antithrombin (A tryn)

Answer 11

Goat

For antithrombin deficiency

Question 12

The difference between the template and the coding strand

Answer 12

The mRNA is made off of the the template strand and is essence a copy of the coding strand

Question 13

In which direction is DNA synthesised?

Answer 13

DNA is read and synthesised 5’ to 3’

Question 14

Poly/monocistronic

Answer 14

Polycistronic is where a single strand of mRNA can code for more than one polypeptide. Can be organised in an operon (not

Monocistronic is where a mRNA strand can code for only one polypeptide. The majority of human mRNA is of this type

Question 15

DNA processes: Transformation

Answer 15

Uptake of free DNA

Transfection in animal cells

Question 16

DNA processes: Conjugation

Answer 16

DNA transfer in cell to cell contact

Question 17

DNA processes: Transduction

Answer 17

DNA transfer via virus

Question 18

The three steps in molecular cloning

Answer 18

1. isolate source DNA
2. insert source DNA into cloning vector
3. introduce cloned DNA into host organism

Question 19

Describe the process

Answer 19

Source DNA inserted into a plasmid that has the gene for ampicillin resistance
Mix the plasmids with E.coli and CaCl2 and a pulse of heat
Culture the E.coli on ampicillin plates
Bacteria that take up the plasmids survive, the others don’t
The plasmids will then replicate within the bacteria

Question 20

PCR- polymerase chain reaction

Answer 20

1. Denature the DNA strands (~30secs at 94degrees)
2. Anneal with primers (~30 secs @55-65 degrees)
   The primers will bind upstream and downstream of the desired gene and will elongate from there
3. Elongate with thermostable DNA polymerase (1 min per kb @ 72 degrees)

Do this n times and the number of copies of DNA gained is 2^n

Question 21

MCS and LacZ

Answer 21

Can tell which bacteria have taken up plasmids as those that don’t die but cannot tell whether plasmid has taken up source DNA. This can be done through the use of the lacZ gene.

Question 22

Explain the LacZ identification

Answer 22

LacZ gene codes for Beta galactosidase which degrades lactose and contains the MCS (site where the source DNA goes)

If the source DNA is taken up then the LacZ gene becomes inactive, if not it remains active

To test whether source DNA was taken up X-gal is added. If LacZ is active then X-gal turns blue

Hence the bacteria will do the following:
If the bacteria has taken up the plasmid and the plasmid contains the source DNA= white cultures
If the bacteria has taken up the plasmid but the source DNA is not in the plasmid= Blue cultures
If the bacteria has not taken up the culture=it dies, due to it not having ampicillin resistance

Question 23

Why are proteins such as antithrombin/factor VIII not produced in bacteria?

Answer 23

Bacteria generally cannot take glycosylated proteins

The genes usually have large numbers of introns