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FLC > DNA Synthesis > Flashcards

DNA Synthesis Flashcards

1
Q

What type of replication does DNA undergo?

A

Semi conservative

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2
Q

What is a replication origin?

A

The specific site where DNA replication is initiated when

recognised by an initiation complex

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3
Q

What is a replication bubble?

A

Where the DNA unwinds to allow access to the replication machinery

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4
Q

How many replication origins are there in mammalian

DNA replication strands?

A

Multiple

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5
Q

How are the bubbles removed from the strands?

A

Eventually they coalesce and produce 2 daughter

chromosomes

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6
Q

When does DNA synthesis occur?

A

(Synthesis) Phase S

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7
Q

How long does the mammalian cell cycle last?

A

16-24 hrs

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8
Q

What are the phases of the mammalian cell cycle

A

M phase, G1, G2 and S phase

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9
Q

Why is the mammalian cell cycle longer than bacterial?

A

Mammalian DNA contains many more chromosomes

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10
Q

In bacterial DNA, how many replication origins are there?

A

one

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11
Q

Which enzyme synthesises new DNA strands?

A

DNA polymerase

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12
Q

Name the different types of Polymerases used in

bacterial DNA replication and their functions

A

DNA Polymerase I - repair
DNA Polymerase II - repair
DNA Polymerase II - repair

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13
Q

What are the different polymerases and their functions

in eucaryotes?

A 
ɒ alpha - replication 
Β beta - replication 
ɣ gamma - mitochondrion
δ delta - causes elongation
𝜺 epsilon - elongation
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14
Q

List the essential features of DNA polymerase

A
  • Acts in a 5’ - 3’ direction
  • uses AT and GC base pairing
  • Requires a DNA template or primer
  • Has proof reading functions
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15
Q

What requirements need to met before replication can begin?

A

OH on 3C
4 dNTPs
Magnesium ions

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16
Q

What are dNTPs?

A

Deoxyribonucleoside triphosphates

  • Building blocks of DNA
    e. g. dATP, dGTP, dCTP, dTTP
17
Q

How is the sugar phosphate backbone formed?

A

Hydroxyl group attacks the 1st Phosphate
causes release of pyrophosphate
leaving 1 phosphate to react with the hydroxyl to form the
backbone

18
Q

Why is one DNA strand formed discontinuously?

A

DNA polymerases only work in 5’ - 3’ direction
- one strand will be made continuously
the other = discontinuous

19
Q

Where is a replication fork found?

A

At the replication origin

20
Q

What is the lagging strand?

A

3’ - 5’ strand - DNA pol. works in opposite direction so a

primer has to be laid down over again

21
Q

What does the reinitiating of replication multiple times form?

A

Okazaki fragments

22
Q

Define okazaki fragments

A

Short newly synthesised DNA strands formed on the lagging strand

23
Q

What is the role of DNA helicase?

A

Unwinds double helix

24
Q

What does topoisomerase do?

A

Removes coils in the DNA

25
Q

Describe the role of Primase enzyme

A

Lays down some RNA so DNA polymerase knows where

replication starts

26
Q

What is the role of binding proteins?

A

Stabilise the single stranded DNA, preventing reannealing

27
Q

Explain the role of repair DNA polymerase

A

Repairs fragments and removes RNA

28
Q

What does the enzyme DNA ligase do?

A

Splices fragments together

29
Q

Why is the DNA replication error rate so low?

A

DNA polymerase has proof reading and mismatching

repair systems

30
Q

What can happen if defects are inherited?

A

Can cause cancer

31
Q

What is the significnce of DNA replication inhibitors?

A

They are important agents for

  • antiviral
  • antibacterial
  • antitumour
32
Q

Give examples of DNA replication inhibitors

A

Antibacterial (Gyrase inhibitors)
- ciprofloxacin, levofloxacin, novabiocin

Antitumour (Topoisomerase II inhibitors)
- etoposide, doxorubicin, mitoxantrone

Antiviral (reverse transcriptase)
- AZT

FLC (34 decks)

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