1.2

Question 1

Requirements for DNA replication

Answer 1

• DNA nucleotides
• Two template strands
• DNA polymerase
• Ligase
• Primers

Question 2

DNA nucleotides used for

Answer 2

They are added to form the two new strands of DNA

Question 3

What are two template strands used for

Answer 3

To allow DNA to be copied onto

Question 4

What is DNA polymerase used for

Answer 4

Adds DNA nucleotides to deoxyribose sugar at 3’ end of newly forming strand

Question 5

What is ligase used for

Answer 5

Joins fragments of DNA together

Question 6

What are primers used for

Answer 6

Starting DNA replication by binding to 3’ end of template strand so DNA polymerase can add DNA nucleotides

Question 7

What is a primer

Answer 7

Short strand of DNA nucleotides

Question 8

How is the leading strand replicated

Answer 8

continuously

Question 9

How is the lagging strand replicated

Answer 9

In fragments

Question 10

Why leading and lagging strands

Answer 10

DNA polymerase can only add nucleotides to the 3’ end

Question 11

Step 1 leading strand

Answer 11

DNA unwound and unzipped to break hydrogen bonds between bases and form two template strands

Question 12

Step 2 leading strand

Answer 12

Primers attach to the 3’ end of leading strand and replication starts

Question 13

Step 3 leading strand

Answer 13

DNA polymerase adds nucleotides using complementary base pairing to the 3’ end of template strand

Question 14

Step 1 lagging strand

Answer 14

Lots of primers used on 5’ ends as the strand is exposed (as the other one replicates)

Question 15

Step 2 lagging strand

Answer 15

DNA polymerase adds DNA nucleotides to deoxyribose sugar 3’ end in fragments

Question 16

Step 3 lagging strand

Answer 16

Ligase joins the fragments of DNA

Question 17

PCR (polymerase chain reaction)

Answer 17

Is a technique for the amplification of DNA in vitro (outside cell)

Question 18

Requirements for PCR

Answer 18

• DNA template strand
• Heat tolerant DNA polymerase
• DNA nucleotides
• Primers
• pH buffer

Question 19

Uses of PCR

Answer 19

• Settling paternity suits
• Solving crimes
• Diagnosing genetic disorders

Question 20

What happens in PCR

Answer 20

Primers are complimentary to specific target sequences so attach at the 2 ends of the region of DNA to be amplified

Question 21

Stage 1 PCR temperature

Answer 21

92 - 98

Question 21

What happens stage 1 PCR

Answer 21

Heat breaks hydrogen bonds to separate strands

Question 22

Stage 2 PCR temperature

Answer 22

50 - 65

Question 23

What happens stage 2 PCR

Answer 23

Cooled so primers can bind to complimentary target sequences

Question 24

Stage 3 PCR temperature

Answer 24

70 - 80

Question 25

What happens stage 3 PCR

Answer 25

DNA heated for heat tolerant DNA polymerase to replicate the region of DNA

Question 26

Gel electrophoresis is a technique used to

Answer 26

Separate DNA strands of different lengths

Question 27

What happens in gel electrophoresis

Answer 27

DNA is placed in small wells at the top of an agarose gel, and an electric field applied, then the current is switched on and the DNA is attracted to the positive electrode

Question 28

Why DNA attracted to positive electrode

Answer 28

Due to its negative charge

Question 29

Why does gel electrophoresis work

Answer 29

The longer a piece of DNA, the harder it is for it to move through the gel - so the larger fragments are found nearer the wells, whilst the smaller fragments move faster and are located at the positive elecctrode at the opposite side of the wells

Question 30

What must DNA be for gel electrophoresis

Answer 30

Stained before it can be visualised in the gel