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Flashcards in DNA lecture 1 Deck (29):
1

What did Watson and Crick Propose

Semi-conservative replication.
- Parent strand
-Daughter strand

Hybrids of the new and old strand

2

Who proved the Watson and Crick hypothesis?

Messelson and Stahl who conducted an experiment using radioactive nitrogen taken up within Ecoli.

3

What did the experiment involve?

Centrifuged the Ecoli bacteria and then measured the density of the resulting DNA strands. Radioactive 15N has a greater density and would sink to the bottom of the test tube.
Then would compare by the degree of sinking within the test tube:
- Parent strand vs Daughter Strand vs Hybrid strand

4

What determines where DNA replication occurs in eukaryotic cells?

The origins of replication

5

What is involved within DNA replication

To antiparallel complementary DNA strands

6

What determines the direction of the DNA strands?

Sugar in the carbons - exposed 3` OH group

7

What initiates DNA replication

DNA polymerase III = polymerisation of nucleotides

8

What does DNA Polymerase III require?

4 dNTPs, template strand & primer with 3` OH group

9

What makes RNA Primers

RNA Primase/ polymerase

10

What direction is complementary DNA strands synthesised in

5` to 3`

11

What direction do the DNA enzymes move in?

3` to 5`

12

Does one or both strands act as templates

Both strands behave as templates

13

What are two important components of semi-conservative replication

Bidirectional and simultaneous DNA replication

14

What do we need to overcome in DNA replication synthesis

The need for complementary strands to be made 5` to 3. We overcome this through discontinuous synthesis.

15

What is it easier to make a complementary DNA strand for: leading or lagging strand

Leading strand = continuous synthesis

16

What are the DNA fragments called that are made in discontinuous DNA synthesis

Okazaki fragments

17

How did we prove the Okazaki fragments presence?

Okazaki used H3-dnTP (ie radioactive) which was incorporated into the presence of the DNA for 5 second pulses. Break up strands and found more H3 in continuous strand of leading strand and less in the lagging strand during discontinuous synthesis in DNA replication.

18

What does helicase do

Unwinds DNA double helix by breaking double bonds between complementary DNA base pairs

19

What form of DNA polymerase is responsible for exonuclease activity?

DNA Polymerase I

20

What does DNA polymerase I do?

locates and removes RNA primers

21

What does DNA ligase do?

Adds phosphate into the gaps of the phosphate sugar backbones, where the RNA primers originally where.

22

What does RNA Primers initiate?

DNA replication

23

What do we call the protein complex of DNA replication

Replisome

24

What determines the origin of replication

Regions where there are lots of adenine and thymine nitrogenous bases = 2 hydrogen bonds and therefore easier to separate.

25

Does proof reading occur

Yes

26

Number of template strands

2

27

Size of templte

Whole strand of complementary DNA

28

Products

DNA

29

Nucleotide substrate

dNTPs