Exam 4: DNA Replication Flashcards
What are the 3 phases of DNA replication?
- Initiation
- Elongation
- Termination
In what direction does replication proceed?
Outward (bidirectionally)
What bonds need to be broken to separate the DNA strands without destroying them?
H bonds
What unwinds DNA?
DNA helicase
What does DNA helicase use to unwind DNA?
ATP
What is SSB?
Single-Stranded DNA Binding Protein
What is the role of SSB?
Prevents renaturing or formation of loops of single strands after helicase moves through
What does topoisomerase do?
It cuts and rejoins DNA
Why is topoisomerase critical?
It relieves tension in the helix
Is DNA topoisomerase ahead of or behind the replication fork?
Slightly ahead of
What are the two requirements for the initiation of DNA synthesis?
- There must be a nucleic acid primer
- DNA polymerase III adds nucleotides to the 3’ end of the primer
Why do a few nucleotides (primer) bond to the template strand?
This provides a free OH group that can combine with an incoming dNTP to form a phosphodiester bond
Primase is a type of …
RNA polymerase
What does primase synthesize?
A short RNA segment that serves as a primer
How many primers are needed in the leading strand?
1
DNA is synthesized as one continuous molecule in which strand?
Leading strand
What is the name for how DNA is synthesized in the lagging strand?
Okazaki fragments
What removes RNA primers at the beginning of each Okazaki fragment?
DNA polymerase I
What joins adjacent DNA fragments?
DNA ligase
What covalently links Okazaki fragments?
DNA ligase
What is responsible for DNA synthesis around the replication fork?
Replisome
What is the problem with the synthesis at the end of the lagging strand?
There is nothing to replace the last primer
What are the regions at the ends of linear chromosomes?
Telomeres
What is the role of telomerase?
Adds more repeating bases to the end of the lagging strand
