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Biology > 1.2 - Replication of DNA > Flashcards

1.2 - Replication of DNA Flashcards

1
Q

Explain why DNA replication is described as semi-conservative?

A

It has one new and one original strand

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2
Q

Why is DNA replication required?

A

Before mitosis to ensure that both daughter cells get an identical copy of the genetic information from the parent cell.

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3
Q

What is required in order for DNA replication to take place?

A

DNA polymerase and ligase (enzymes), DNA nucleotides, primers, template DNA, ATP

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4
Q

Which bonds are broken to separate the two strands of DNA?

A

Hydrogen bonds

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5
Q

Why can DNA only be replicated in one direction?

A

Because DNA polymerase can only add DNA nucleotides to the 3’ end of the new DNA strand which is forming.

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6
Q

What is meant by discontinuous synthesis of the lagging strand?

A

Strand is replicated in fragments

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7
Q

What is a primer?

A

a short strand of nucleotides which binds to the 3’ end of the template DNA strand allowing DNA polymerase to add nucleotides.

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8
Q

What is the function of a primer?

A

To provide a start point for DNA polymerase.

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9
Q

Why are there multiple replication forks on one strand of DNA?

A

To allow speedy replication.

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10
Q

Why is there a leading and lagging strand in DNA replication?

A

Parent strands are anti-parallel but DNA polymerase can only add DNA nucleotides to the 3’ end of the new DNA strand which is forming.

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11
Q

What is the first stage of enzyme control of DNA replication?

A

After the hydrogen bonds break, the DNA separates.

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12
Q

What is the second stage of enzyme control of DNA replication?

A

A DNA primer (a short stretch of complementary nucleotides) attaches to the start of the piece of DNA being copied

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13
Q

What is the third stage of enzyme control of DNA replication?

A

DNA polymerase then attaches free nucleotides to the 3’ end of the primer

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14
Q

What is the fourth stage of enzyme control of DNA replication?

A

This is a continuos process until leading strand is copied

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15
Q

What is the function of PCR?

A

To amplify a sequence of DNA.

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16
Q

What are the requirements of PCR?

A

Template DNA, heat-tolerant (taq) DNA polymerase, primers, free DNA nucleotides.

17
Q

When is PCR used?

A

Crime scene analysis to identify suspects, paternity testing and diagnose genetic disorders.

18
Q

Why is DNA heated in the first stage of PCR ?

A

To break the hydrogen bonds between the bases and separate the two strands.

19
Q

Why is DNA cooled during the second stage of PCR?

A

To allow primers to bind/anneal to target sequences.

20
Q

Why is heat-tolerant DNA polymerase used in PCR?

A

It doesn’t denature during the heating cycles.

21
Q

Why is DNA heated back up for the third stage of PCR?

A

To allow heat-tolerant DNA polymerase to replicate the region of DNA.

22
Q

What are the primers used in PCR?

A

they are short strands of nucleotides which are complimentary to specific target sequences at the two ends of the region of the DNA to be amplified.

23
Q

What temperature does the first stage of PCR occur at?

A

92-98°C

24
Q

What temperature does the second stage of PCR occur at?

A

50°C- 65°C

25
Q

What temperature does the third stage of PCR occur at?

A

70-80°C

26
Q

What is the difference between DNA polymerase and heat-tolerant polymerase?

A

DNA polymerase denatures at lower temperatures than heat-tolerant polymerase.

27
Q

Which bonds are synthesised by DNA / heat-tolerant DNA polymerase?

A

Strong chemical bonds / covalent bonds between sugar and phosphates of adjacent nucleotides.

28
Q

Which rule allows the molecules of DNA to be copied?

A

Complementary base pairing rule

29
Q

List 3 uses of DNA amplified through PCR

A
  1. Solve crimes
  2. Settler paternity suits
  3. Diagnose genetic disorders
30
Q

Why does the lagging strand have to be copied in fragments?

A

Because DNA polymerase can only add DNA nucleotides in a 5’ to 3’ direction

31
Q

Why are two types of primer needed in PCR?

A

To flank the target region of DNA

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