D1.1 Replication

Question 1

When is DNA replication carried out in eukaryotic cells?

Answer 1

Before mitosis and meiosis

Question 2

What is DNA replication before mitosis required for?

Answer 2

Growth and tissue replacement

Question 3

What is DNA replication before meiosis required for?

Answer 3

Reproduction

Question 4

What allows for the high degree of accuracy in DNA replication?

Answer 4

Complementary base pairing

Question 5

Meselson and Stahl Experiment

Answer 5

• Proved that DNA replication is semi-conservative
• Grew many generations of E.coli cells in a medium containing only heavy nitrogen (15N). Created a low band when centrifuged.
• DNA was then introduced to a medium with only light nitrogen (14N).
• After one generation the band was higher.
• After the 2nd gen, there was 2 bands one for hybrid DNA and one for the DNA with only light nitrogen

Question 6

Steps of DNA replication

CHECK!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Answer 6

• Coiled DNA is allowed to uncoil
• The double helix is unwound by DNA gyrase
• Helicase “unzips” the rungs of DNA by breaking the weak hydrogen bonds
• New pieces of DNA are formed from free nucleotide units by DNA polymerase
• The free nucleotides are matched up by complementary base pairing

Question 7

What is the advantage of complimentary base pairing in DNA replication?

Answer 7

It allows almost perfect/identical copies to be made, ensuring mutations are avoided as often as possible.

Question 8

DNA replication is semi-conservative, what does this mean?

Answer 8

Semi-conservative essentially means 1/2 original. This means that the original strand is split in half and a new half to each strand is formed via complementary base pairing. This leaves you with two new strands each containing half the original strand of DNA.

Question 9

What is DNA amplicfication?

Answer 9

Tiny pieces of DNA being copied many times to form billions f copies of that DNA. Can be done with the Polymerisation chain reaction (PCR)

Question 10

What is required for PCR?

Answer 10

• The DNA to be amplified
• Buffer solution
• Primers
• Taq DNA polymerase
• DNA nucleotides (ATCG)

Question 11

What is the role of Buffer solution in the PCR?

Answer 11

It allows the necessary reactions to occur by keeping the pH suitable for the enzymes.

Question 12

What is the role of primers in the PCR?

Answer 12

Primers are the complimentary sequence to the DNA you want replicated.

Question 13

What is the role of Taq DNA polymerase in the PCR?

Answer 13

It attaches to the primer and creates a new strand of DNA nucleotides by complimentary base pairing. It can tolerate the high temps used to speed up the rate of rxn.

Question 14

Steps in the polymerisation chain reaction (PCR)

Answer 14

• Denaturing (strands split in 1/2)
• Annealing (Primers attatch
• Extension (A new strand is synthesised)
• DNA is cut into fragments by restriction enzymes before analysis

Question 15

What is Gel electrophoresis used for?

Answer 15

To seperate proteins or DNA fragments by size.

Question 16

Steps of Gel electrophoresis

Answer 16

• An agarose gel with wells in it is placed in a chamber that allows electricity to be pass through the gel
• The prepared DNA is injected into the wells
• The electrodes are turned on, causing the DNA to move towards the positive electrode (DNA IS strongly neg)
• The size of the DNA can be calculated by the rate of travel

Question 17

Common applications for PCR and gel electrophoresis

Answer 17

Forensic analysis and paternity testing.