Lecture 5 DNA Replication I Flashcards
How can DNA replication be visualized
By use of modified nucleotides, which can be radioactively labelled, so that they fluoresce under UV light, allowing DNA to be visualized.
When new DNA strands are synthesized at the replication fork, this process is known as….?
DNA dependant DNA synthesis, because DNA is the template.
In which direction does DNA synthesis always occur?
5’ to 3’ direction.
Which enzyme is responsible for DNA dependant DNA synthesis
DNA dependent DNA polymerase.
What are the names of the DNA polymerases in bacteria
DNA polymerase I
DNA polmyerase III
Which is the main replicating enzyme in bacteria
DNA polymerase III
DNA polymerase III has which exonuclease activity
Has 3’5’ exonuclease activity only
DNA polymerase I has which exonuclease activity
Has both 3’5’ and 5’3’ exonuclease activity
What are the names of the replicating polymerases in eukaryotes
DNA polymerase alpha
DNA polymerase delta
Which is the main replicating enzyme in eukaryotes
DNA polymerase delta
dna polymerase alpha has which activity
neither 3’5’ or 5’3’ exonuclease activity
dna polymerase delta has which activity
has 3’5’ exonuclease activity only.
What is required for DNA synthesis in bacteria
a Primer made from RNA.
How are primers produced in bacteria
Primase enzyme synthesises them.
In bacteria, how is the leading strand synthesized
RNA primer binds first. DNA polymerase III continues to synthesize the rest of the new strand.
In eukaryotes, how is the leading strand synthesized
- RNA Primer binds.
- DNA pol alpha extends primer and adds the first 15-20 nucleotides.
- DNA polymerase delta continues to synthesize the rest of the strand.
In which direction does DNA synthesis always take place
5’3’ direction.
The leading strand ….
Can be copied by continuous DNA synthesis.
copying of leading strand requires an RNA primer.
What is a key feature held by most DNA polymerases
- Most can also degrade DNA
- This is called exonuclease activity.
What are the two types of Exonuclease activity that DNA polymerases have
3’5’ exonuclease activity (proofreading)
5’3’ exonuclease activity
Explain what is meant by 3’5’ Exonuclease activity
- proofreading ability
- polymerase can remove nucleotides it has just inserted.
- allows errors to be corrected.
Explain what is meany by 5’3’ exonuclease activity
- polymerase can remove DNA already attached to the template.
What are the roles of Single strand binding proteins
- to prevent the seperated strands from re-attatching
- to protect strands from exonuclease activity.
Name an example of a single strand binding protein in Eukaryotes.
Replication protein A
State the functions and structure of DNA polymerase I and III in bacteria
polymerase I is responsible for repair
pol III is the main replicating enzyme
State the functions and structure of DNA Polymerase alpha and delta in eukaryotes
Pol alpha is
Pol delta is the main replicating enzyme