4.1

Question 1

DNA copies itself with great accuracy, because of 2 things:

Answer 1

• Base-pairing rules

- ‘Proofreading’ carried out by the enzyme DNA polymerase

Question 2

PCR stands for:

Answer 2

Polymerase Chain Reaction

Question 3

PCR is a method of

Answer 3

replicating many copies of DNA in a test tube

Question 4

PCR is very useful in research when a sample of DNA may be extremely

Answer 4

tiny

Question 5

PCR is usually carried out in very small tubes in a machine called a

Answer 5

thermocycler

Question 6

PCR is very similar to semi-conservative DNA replication inside cells, except that heat is used to

Answer 6

break open the hydrogen bonds between the bases in the DNA double helix

Question 7

PCR uses primers to mark the

Answer 7

beginning and end of the section of DNA to be copied

Question 8

Primers are:

Answer 8

short single-stranded nucleic acid sequences, about 20 nucleotides long

Question 9

PCR also uses

Answer 9

DNA polymerase

Question 10

Because heat is needed to split the DNA into single strands, a special heat-stable DNA polymerase is used. This is obtained from

Answer 10

bacterium that lives in hot springs

Question 11

To carry out PCR, the sample of DNA to be copied is placed in a test tube, together with:

Answer 11

• DNA polymerase enzyme
• Primers
• DNA nucleotides

Question 12

First stage of PCR is:

Answer 12

• mixture is heated to 93 degrees C

- this breaks the hydrogen bonds between the 2 strands of DNA and makes the DNA single-stranded

Question 13

Second stage of PCR is:

Answer 13

• DNA is cooled to 55 degrees C
• This allows the 2 primers to attach to the ends of the DNA sequence that needs to be copied on the separated DNA strands
• primer is an attachment to signal to a polymerase where to start synthesising new DNA

Question 14

Third stage of PCR is:

Answer 14

• DNA is then heated to 72 degrees C (optimum temp. for DNA polymerase enzyme used)
• Enzyme joins new nucleotides on to the DNA strands, producing 2 identical molecules from the original DNA
• 2 polymerase molecules attach to the 2 primers on the 2 DNA strands and move along the strand
• As the primers move along they create new complementary DNA

Question 15

The whole PCR cycle takes about 2 minutes and is repeated as many times as

Answer 15

necessary

Question 16

3 stages of PCR are:

Answer 16

1- DENATURATION OF DNA
2-ANNEALING THE DNA
3-EXTENSION OF DNA

Question 17

What does PCR enable us to do?

Answer 17

• Produce large quantities of DNA from very small samples in a remarkably short time
• Helps us to analyse tiny samples of DNA

Question 18

7 uses of PCR:

Answer 18

1- Infection detection
2-Genetic testing
3-Cancer warning
4-Tissue matching
5-Forensic medicine
6-Genetic analysis
7-Fossils and mummified remains

Question 19

1-Infection detection uses PCR to:

Answer 19

• Amplify the DNA from a single bacterium or virus
• Can provide a speedy and accurate diagnosis
• Enabling right treatment quickly

Question 20

2-Genetic testing uses PCR to:

Answer 20

• Easier to identify individuals who carry the genes that can cause problems like CF and muscular dystrophy
• May be used to develop tests for the genetic variations

Question 21

3-Cancer warning uses PCR to:

Answer 21

-Amplify DNA to detect the genetic changes that take place in cancerous cells very early in the development of cancer

Question 22

4-Tissue matching uses PCR to:

Answer 22

-Close tissue match between donor and recipient reduces the chance that the new organ will be rejected

Question 23

5-Forensic medicine uses PCR to:

Answer 23

-Amplify DNA at a crime scene

Question 24

6-Genetic analysis uses PCR to:

Answer 24

-Making many copies of the DNA extracted from a single embryo cell, so that enough DNA can be obtained

Question 25

7-Fossils and mummified remains uses PCR to:

Answer 25

-Make many copies of the tiny quantity of DNA that can be extracted from fossils and mummified remains