D1.1 DNA REPLICATION

Question 1

DNA Replication

Answer 1

The synthesis of new strands of DNA with the same base sequence as original strand.

Question 2

Why is DNA Replocation needed?

Answer 2

So that both daughter cells have the entire genome.

Question 3

What 3 processes is cell division a part of?

Answer 3

• Growth
• replacement of damaged tissue.
• reproduction, providing cells that become gametes.

Question 4

What is DNA described as?

Answer 4

Semi-conservative

Question 5

why is DNA called Semi-conservative?

Answer 5

Each DNA molecule has one old strand and one new strand.

Question 6

Why are the two strands of DNA identical to each other in base sequence?

Answer 6

Complementary base pairing.

Question 7

Why is complementary base pairing important?

Answer 7

Ensures dna rep is accurate.

Question 8

Replication fork:

Answer 8

site where a parent DNA molecule is separated into 2 single strands. §

Question 9

Outline DNA replication in steps:

Answer 9

1) Helicase unwinds double helix and breaks H-bonds.
2) DNA polymerase links existing nucleotides to form new strands using the old one as a template strand.
3) New DNA molecule rewinds into double helix.

Question 10

What is PCR used for?

Answer 10

copying DNA artificially

Question 11

where is PCR carried out in?

Answer 11

small tubes called eppendorfs.

Question 12

What do Eppendorfs contain?

Answer 12

• DNA sample
• Taq DNA Polymerase, heat-stable enzyme, allows higher temps to be used.
• Primers: short DNA fragments that bind to DNA sample§s after being split by heat.
• DNA nucleotides for assembling new strands.

Question 13

How many primers are needed?

Answer 13

2

Question 14

Outline the temp change cycle of PCR

Answer 14

1) DNA heated to 95 to separate the 2 strands.
2) Temp increased 73 which encourages Taq DNA to replicate both strands starting at the primer.
3) Temp reduced to 53, primers can bind to both strands next to desired sequence.

Question 15

DNA Amplification

Answer 15

There are twice as many copies of a desired DNA base sequence.

Question 16

Gel Electrophoresis

Answer 16

Separating method for charged DNA fragments with different sizes.

Question 17

Outline the procedure of Gel Electrophoresis:

Answer 17

1) A mixture of macromolecules is placed on a thin sheet of gel (mesh of inert material such as agarose).
2) Electrodes are attached at both ends.
3) DNA moves to the negative end because phosphate groups are negatively charged.
4) Small molecules move faster than large ones.

Question 18

What are the uses of Gel Electrophoresis?

Answer 18

Separating DNA with short tandem repeats.

Question 19

How are PCR and Gel Electrophoressi applied for DNA profiling:

Answer 19

1) DNA sample is taken
2) Primers are used to create to promote simultaneous amplification of 15 STRs by PCR.
3) STRs are separated by Gel electrophoresis.

Question 20

What are applications of PCR and gel electrophoresis?

Answer 20

• Forensic investigations
• Paternity tests

Question 21

In what direction does DNA replication occur:

Answer 21

DNA Polymerase III adds free nucleotides to the deoxyribose at the 3’ terminal/

Question 22

The two DNA strands are…

Answer 22

ANTI-PARALELL

Question 23

Compare Leading and Lagging Strands of DNA:

Answer 23

1) Leading Strand:
- replication is continuous
- DNA polymerase moves towards the replication fork.
2) Lagging Strand
- DNA Polymerase III moves away from the replication fork.
- Short DNA fragments called Okazaki fragments are used to replicate the strand.
- discontinuous replication.

Question 24

Helicase function

Answer 24

• unwinds double helix - separates strands

Question 25

DNA Primase

Answer 25

Adds a RNA primer to dna strand

Question 26

DNA Polymerase III Func

Answer 26

Binds to lagging strand at 3’ end of RNA primer + adds DNA nucleotide.

Question 27

DNA Polymerase I

Answer 27

Removes RNA Primer and replaces it with DNA, leaves a gap.

Question 28

DNA Ligase

Answer 28

Seals up the gap made by DNA polymerase, makes sugar-phosphate bond

Question 29

DNA Primase (Func - Leading)

Answer 29

Adds primer to 3’ to 5’ end, DNA polymerase can bind

Question 30

DNA Polymerase III

Answer 30

Moves toward replication fork and adds free nucleotides to assemble DNA.

Question 31

DNA Proofreading

Answer 31

DNA Polymerase III moves back to the mismatched pair, excises it and re-inserts a nucleotide with a correct base.