Replication of DNA Flashcards
What enzyme is responsible for DNA replication?
DNA polymerase
What is the function of a primer?
To provide a start point for DNA polymerase.
Why is DNA replication required?
Before mitosis to ensure that both daughter cells get an identical copy of the genetic information from the parent cell.
What is required in order for DNA replication to take place?
Enzymes, DNA nucleotides, primers, template DNA, ATP
Which enzyme joins the fragments of DNA on the lagging strand?
Ligase
Which bonds are broken to separate the two strands of DNA?
Hydrogen bonds
Why can DNA only be replicated in one direction?
Because DNA polymerase can only add nucleotides to the 3’ end.
What is meant by discontinuous synthesis?
Strand is replicated in fragments
What is meant by continuous synthesis?
Whole strand is made in one piece.
What is the function of PCR?
To amplify a sequence of DNA.
What are the requirements of PCR?
Template DNA, taq polymerase, primers, free DNA nucleotides, buffer
When is PCR used?
Crime scene analysis to identify suspects, paternity testing, identifying evolutionary relationships.
Why are there multiple replication forks on one strand of DNA?
To allow speedy replication.
Why is DNA heated in the first stage of PCR?
To break the hydrogen bonds between the bases and separate the two strands.
Why is DNA cooled during the second stage of PCR?
To allow primers to anneal to the template strands.
Why is taq polymerase used in PCR?
It doesn’t denature during the heating cycles.
Why is DNA heated back up for the third stage of PCR?
To allow taq polymerase to synthesise the new strands of DNA.
Why are two different primers needed during PCR?
One which is complementary to each strand being copied.
What temperature does the first stage of PCR occur at?
94-96°C (any within range)
What temperature does the second stage of PCR occur at?
55°C and 65°C (any within range)
What temperature does the third stage of PCR occur at?
72°C
Why is there a leading and lagging strand in DNA replication?
Parent strands are anti-parallel but DNA can only be synthesised in 5’ - 3’ direction.
What is the difference between DNA polymerase and taq polymerase?
DNA polymerase denatures at lower temperatures than taq polymerase.
What is meant by a negative control in PCR?
Doing it without DNA sample to ensure no contamination.
What is meant by a positive control in PCR?
Doing it with a sample of DNA you know will copy to ensure everything is working.
Which bonds are synthesised by DNA / taq polymerase?
Strong chemical bonds / covalent bonds between sugar and phosphates of adjacent nucleotides.
Which rule allows the molecules of DNA to be copied?
Complementary base pairing rule
Which strand in DNA replication requires the use of many primers?
Lagging strand
