PCR Ploymerase Chain Reaction

Question 1

What is PCR?

Answer 1

PCR is a laboratory technique that is used for the amplification of DNA in vitro.

Question 2

What does this mean that it is done in vitro?

Answer 2

It means PCR is used to make many copies of a section of DNA outside of the body.

Question 3

What does the uses of PCR include?

Answer 3

Forensics e.g:

1. Identify a suspect from blood or semen sample.
2. Testing for genetic disease.
3. paternity testing.
4. Investigate plant evolution using chloroplast DNA.

Question 4

What does PCR involve?

Answer 4

The use of primers

Question 5

What is the process of PCR?

Answer 5

1. DNA is heated to 93•C. This cause the DNA to denature and the strands to separate.
2. DNA is cooled to 55•C to allow the complementary primers to bind to the specific target sequence. ( it makes primers bond to the separate DNA strands).
3. Temperature is then increase to over 70•C and heat tolerant DNA polymerase is used to add nucleotides to the primers therefore replicating the section of DNA.

Question 6

What happens to the number of DNA fragments?

Answer 6

It’s doubled in each cycle

Question 7

What are the requirements for PCR?

Answer 7

1. Primers
2. supply of nucleotides
3. pH buffer
4. Mg2+ - DNA polymerase co-factor (makes the polymerase work better)

Question 8

What controls should be used when setting up PCR?

Answer 8

Positive and negative controls

Question 9

Describe a negative control?

Answer 9

It contains exactly the same substances as the test PCR tube except that it contains no template DNA.

Question 10

What is the purpose of the negative control?

Answer 10

To check that there is no contamination of the tubes.

Question 11

Describe the positive control?

Answer 11

It contains the same components as the sample but it also contains a template that is guaranteed to be amplified using PCR.

Question 12

What is the purpose of the positive control?

Answer 12

To verify negative amplification results.