DNA Replication and Repair

Question 1

Describe DNA

Answer 1

Double helix, strands run anti-parallel, sugar-phosphate backbone on the outside, complementary base pairs

Question 2

Name the 3 replication patterns

Answer 2

Semiconservative, conservative, dispersive

Question 3

Describe semiconservative

Answer 3

parent serves as a template and new molecules have one old and one new strand

Question 4

Describe conservative

Answer 4

original helix serves as a template

Question 5

Describe dispersive

Answer 5

parent fragments serve as template, assembling old and new parts into molecules

Question 6

How many hydrogen bonds do A and T complimentary bases have?

Answer 6

2

Question 7

How many hydrogen bonds do C and G complimentary bases have?

Answer 7

3

Question 8

In what direction do replication forks move in?

Answer 8

Bi-directionally

Question 9

What is the name given to the originating region of a chromosome?

Answer 9

Origin of replication or ori

Question 10

What does DNA replication start with?

Answer 10

Short primer

Question 11

What is the enzyme that synthesises the primer DNA one nucleotide at a time?

Answer 11

Primase

Question 12

DNA polymerase adds nucleotides to what end of the primer?

Answer 12

3’ end

Question 13

What molecule uses energy from ATP hydrolysis to unwind DNA?

Answer 13

DNA helicase

Question 14

What direction is the leading strand synthesised?

Answer 14

5’-3’

Question 15

What direction is the lagging strand synthesised?

Answer 15

5’-3’

Question 16

What is used to replicate the lagging strand in small fragments?

Answer 16

Okazaki Fragments

Question 17

DNA polymerase III adds nucleotides to what end?

Answer 17

3’

Question 18

DNA polymerase I then replaces the primer with what?

Answer 18

DNA

Question 19

What is the final phosphodiester linkage between fragments catalysed by?

Answer 19

DNA ligase

Question 20

What is PCNA?

Answer 20

Proliferating Cell Nuclear Antigen

Question 21

What are the functions of PCNA?

Answer 21

Helps to orient the polymerase for substrate binding, binds other proteins and removes the pre-replication complex from origin of replication

Question 22

In the replication of linear chromosomes, what leads to cell death?

Answer 22

When the primer nearest the end is removed there is no 3’ end and so this region is removed, and the chromosome is shortened

Question 23

What are the repetitive sequence ends of eukaryotic chromosomes called and what do they do?

Answer 23

Telomeres; they are protective and prolong cell division

Question 24

What is aneuploidy?

Answer 24

An abnormal number of chromosomes; caused by chromosome segregation defects

Question 25

What are the different kinds of structural abnormalities of chromosomes?

Answer 25

Mutations, deletions, amplifications and rearrangements of chromosome segments

Question 26

What are the four checkpoint mechanisms?

Answer 26

Inducers, sensors, transducers, effectors

Question 27

Name the 3 repair mechanisms in DNA

Answer 27

proofreading, mismatch and excision

Question 28

Describe proofreading

Answer 28

if bases are paired incorrectly, the incorrect nucleotide is removed; for errors during replication

Question 29

Describe mismatch repair

Answer 29

detects mismtched bases and repairs them; for uncorrected errors and damage

Question 30

What happens if mismatch repair fails?

Answer 30

DNA is altered and a mutation results

Question 31

Describe excision

Answer 31

enzymes constantly scan DNA for damaged bases and these are excised and DNA polymerase I adds the correct ones