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27 Cards in this Set

  • Front
  • Back
What does a Nucleotide consist of?

1. a Base containing Nitrogen

2. a 5 Carbon Sugar (deoxyribose)

3. one or more Phosphate Groups

a. Phosphate group

b. 5 carbon sugar

c. Nitrogen containing Base

What are the 4 nucleotide bases in DNA?

1. Adenine (A)

2. Thymine (T)

3. Guanine (G)

4. Cytosine (C)

a. In DNA, nucleotides are Covalently linked via _______ bonds to form a phosphate backbone

b. This bond links a _________ to a _________

c. How are 2 parallel polynucleotides chains held together?

a. Phosphodiester


- Phosphate group

- Deoxyribose Sugar

c. via Hydrogen bonds between complementary base pairs

a. Hydrogen bond

b. Phosphodiester bond

What are the 3 models of DNA replication?

- Semi-conservative

- Dispersive

- Conservative

a. Semi-conservative

b. Conservative

c. Dispersive

DNA synthesis begins at replication origins.

a. To be used as a template, what must happen to the DNA double helix?

b. Why is the double helix very stable?


- DNA helix must be 'opened'

- DNA strands must be separated to expose unpaired bases

b. Because there are a large number of (strong) Hydrogen Bonds between bases

a. Replication Origin

b. Initiator Proteins

Replication Fork

a. is DNA replication unidirectional or bidirectional?

b. how many origins of DNA replication do bacteria have?

c. how may origins of DNA replication do eukaryotes have?

d. in bacteria, how many nucleotide pairs does the replication origin span?

a. Bidirectional

b. One

c. Multiple

d. 100 nucleotide pairs

What does DNA Polymerase do in DNA replication?

DNA Polymerase catalyses the addition of nucleotides to the 3' end

a. In which direction does DNA synthesis occur?

b. Which end of a DNA strand do new subunits get added to during synthesis?

a. 5'-3' direction

b. 3' end

What opens up DNA double helix?

DNA Helicase

a. are Okazaki fragments found on the Leading or Lagging strand?

b. How is DNA synthesised on the lagging strand?

a. Lagging strand

b. via Okazaki fragments, in 5'-3' direction, discontinuously

What are the 2 proofreading mechanisms which occur in DNA synthesis?

1. Monitoring

2. Exonucleolytic Proofreading

Describe Monitoring as a DNA proofreading mechanism

DNA polymerase 'double checks' the exact base pairing

Describe Exonucleolytic Proofreading

- Error correction reaction

- DNA polymerase can correct the mismatched nucleotides

The enzyme ____(a)_____ uses ____(b)____ to synthesise____(c)____

a. DNA Primase

b. Ribonucleoside Triphosphates

c. RNA Primers

How are RNA primers made?

DNA Primase uses Ribonucleoside Triphospates to synthesise RNA Primers

Describe the use of DNA Primers in:

a. the leading strand

b. the lagging strand

c. In Eukaryotes, how long do RNA primers tend to be?

a. Primer is only needed at the start of replication

b. New primers are needed continuously

c. 10 nucleotides long

what are the 3 additional Enzymes required for Lagging Strand Synthesis?

1. a Nuclease

2. Repair DNA Polymerase

3. DNA Ligase

In Lagging Strand Synthesis, what do the following do?

a. DNA Primase

b. Repair DNA Polymerase

c. Nuclease enzyme

d. DNA Ligase

a. DNA Primase synthesises RNA Primers

b. Repair DNA Polymerase replaces RNA primers with DNA

c. Nuclease enzymes degrade RNA primers

d. DNA Ligase joins the 3' end of the new DNA fragment to the 5' end of the old DNA fragment

RNA Primers are preffered to DNA primers:

- Primase can begin new polynucleotide chains but it does not ____(a)____

- Primers frequently contain ____(b)____

- RNA Primers are automatically marked as a ____(c)____ and are automatically removed and replaced by DNA primers

a. Proofread

b. Mistakes

c. Suspect Copy

For Replication to occur, the double helix must be unzipped ahead of the replication Fork

a. Why?

b. What are the 2 replication proteins which are required to unzip DNA helix?


- So bases on template strand are exposed

- So incoming Nucleotides can form base pairs with template strand


- DNA Helicases

- Single-strand DNA binding proteins (SSB)

DNA helicase:

a. sits at the front of the replication machine (T/F)?

b. How does DNA Helicase move forward along double helix?

a. True

b. Uses ENERGY from ATP Hydrolysis

a. What do (SSB's) Single-Stranded DNA binding proteins do?

b. Without SSB,s what would happen?


- Through Cooperative binding

- SSB's straighten out the single stranded template strand after DNA helicase has separated strands


- Template strand would contain hairpins, where it has base paired with itself

- so DNA replication would not be able to take place properly