Key Area 2

Question 1

What is DNA replicated by?

Answer 1

DNA Polymerase

Question 2

What does DNA polymerase need to start replication

Answer 2

Primers

Question 3

What is a primer

Answer 3

A primer is a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing the polymerase to add DNA nucleotides.

Question 4

How are 2 template strands formed?

Answer 4

DNA is unwound by the DNA polymerase breaking the hydrogen bonds between the bases forming 2 template strands

Question 5

What is added to the 3’ end of the new strand

Answer 5

DNA polymerase adds DNA nucleotides using complementary base pairing

Question 6

DNA polymerase can only add DNA nucleotides in one direction. What does this result in?

Answer 6

This results in the leading strand being replicated continuously and the lagging strand being replicated in fragments.

Question 7

What are the fragments on the lagging strand joined together by?

Answer 7

Ligase

Question 8

What does PCR do

Answer 8

PCR amplifies DNA using complementary primers for specific target sequences.

Question 9

Describe PCR process

Answer 9

1. DNA Is heated to between 92 and 98 degrees c to separate the strands.
2. It is then cooled to between 50-65 degrees c to allow primers to bind to target sequences.

3.it is then heated to between 70 and 80 degrees c for heat tolerant DNA polymerase to replicate the region of DNA

4. The cycle is then repeated

Question 10

State the requirements for PCR

Answer 10

1. DNA template
   A supply of the 4 types of DNA nucleotides (A,T,C,G)
   3.primers
2. Heat tolerant DNA polymerase (enzyme)
3. A pH buffer (to create optimum conditions for enzyme activity

Question 11

Practical applications for PCR

Answer 11

Settle paternity suits
Help solve crime (forensics)
Diagnose genetic disorder