DNA Replication Flashcards

1
Q

What 3 building blocks make up a nucleotide?

A
  • Nitrogenous base
  • Sugar (deoxyribose/ribose)
  • Phosphate group
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2
Q

What is removed from the deoxy-Base Triphosphate when it is added to the growing DNA strand?

A

2 phosphates

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3
Q

Where does DNA replication begin?

A

Origin of replication

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4
Q

What does DNA helicase require to carry out its role?

A

ATP

- Hydrolyses ATP

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5
Q

What dosingle strand binding proteins do

A
  • Assist helicase

- Stabilise and straighten single strands of DNA

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6
Q

What sequences of DNA do origins of replication usually have?

A

AT rich sequences (easier to open)

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7
Q

What DNA polymerases are found in prokaryotes?

A

DNA polymerase I-IV

  • Polymerase III: Major DNA polymerase
  • Polymerase I: Removes RNA primers
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8
Q

What are the DNA polymerases in eukaryotes?

A

alpha, Beta, gamma, delta, epsilon

- Polymerase y: located in mitochondria

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9
Q

What DNa polymerase in eukaryotes is not located in the nucleus and located in the mitochondria?

A

Polymerase y (gamma)

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10
Q

What makes primers?

A

DNA primase

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11
Q

What do primers contain?

A

RNA not DNA

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12
Q

Where does DNA polymerase add to on the DNA strand the new nucleotide?

A

3’ end

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13
Q

Where does the energy come from to add a nucleotide to the DNA strand?

A

From the 3 phosphates

- 2 phosphates are removed

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14
Q

In what direction are new nucleotides added?

A

5’ to 3’ direction

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15
Q

The eading and lagging strands are oriented in what direction?

A

Leading strand

  • 3’ to 5’ direction
  • Allows the replicating DNA to be added continously in a 5’ to 3’ direction

Lagging strand
- 5’ to 3’ direction

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16
Q

In prokaryotes what enzyme removes the RNA primer /okazaki fragment and replaces it with DNA?

A

DNA polymerase I

17
Q

In eukaryotes what enzyme removes the RNA primer / okazaki fragment and replaces it with DNA?

A

DNA polymerase delta

18
Q

What is the RNA primer known as on the lagging strand?

A

Okazaki fragment

19
Q

WHat is the function of DNA ligase?

A
  • Joins Okazaki fragments

- Creates phosphodiester bonds

20
Q

What is the function of topoisomerase?

A

Prevents DNA tangling

- Breaks DNA then reseals to relieve tension/twists

21
Q

What is the difference between topoisomerase I and II?

A

Topoisomerase I
- Breaks single strands of DNA then reseals

Topoisomerase II
- Breaks double strands then reseals

22
Q

What do quinolone antibiotics target?

A

Prokaryotic topoisomerases

23
Q

What strand replication is continuous and what strand replication is dicontinous?

A

LEading strand
- Continous

Lagging
- Discontinous

24
Q

Why is DNA replication known as being semi-conservative?

A

New DNA: one old strand and one new strand

25
When may DNA polymerase move in a 3' to 5' direction?
To correct an error
26
What enzyme will remove an incorrect nucleotide?
Exonuclease
27
What are telomeres?
Nucleotides found at the end of chromosomes
28
What sequences are found on telomeres?
TTAGGG
29
What cannot attach on telomeres?
RNA primer on lagging strand
30
What does telomerase do?
- Recognises telomere sequences | - Adds these sequences to new DNA strands
31
What genetic material do telomerases use?
RNA which it uses as a template to synthesize telomere DNA
32
What can telomerase also be known as?
RNA-dependent DNA polymerase
33
What enzyme is telomerase similar to that can be found in certain viruses?
Reverse transcriptase
34
What side of the DNA does telomerase bind to? | Explain how telomerase allows the formation/duplication/extension of the telomere
3' flanking end of the telomere - Complementary to telomerase RNA - Bases are then added using RNA as a template - DNA polymerase then adds the NTs to the lagging strand (5' end) in a 5' to 3' (opposite) direction
35
What kind of cells have many telomerase enzymes?
Cells that require controlled indefinite replication - Hamatopoetic stem cells - Epidermis, hair follicles, intestinal mucosa
36
How can telomerase play a role in cancer?
Allows immortality of cells | - Increased telomerase may lead to cancer