DNA Replication Flashcards
What is DNA replication?
Semiconservative
Where does all DNA replication start?
at a Replication Origin
What is a Replicon
Unit that is replicated together
What is Bidirectional Replication
When DNA can replicate in both directions from the replication origin
Which type of semiconservative replication has bidirectional replication?
Theta replication
What types of replication have a circular DNA template?
Theta and Rolling Circle
What replication model has breakage of nucleotide strand?
Rolling Circle
Which type of replication has many numbers of replicons?
Linear eukaryotic
Which type of replication is unidirectional?
Rolling Circle
Which type of replication has the product of two circular molecules?
Theta replication
Which type of replication has multiple circular DNA molecules?
Rolling Circle
Which type of replication has the product of two linear DNA molecules?
Linear Eukaryotic
What is DNA polymerase III in E.coli?
- Responsible for most DNA synthesis
- Responsible for adding nucleotides to most of the genome
- Proofreads with 3’-5’ exonuclease activity
What is DNA polymerase I in E.coli?
- 5’-3’ exonuclease activity to remove RNA primers
- Proofreads with 3’-5’ exonuclease activity
What does 5’ to 3’ polymerase activity mean?
As polymerase adds DNA to a newly synthesized strand; it will add nucleotides to the 3’ end. So the chain will grow 5’ to 3’
What does 3’ to 5’ exonuclease activity mean?
You’re backing up / You’re removing part of the DNA you just added
What does 5’ to 3’ exonuclease activity mean?
You are cutting out DNA ahead
Describe the function of the protein if the DNA codon sequence is NOT mutated
In Normal and High temps, the protein will have normal function
Describe the function of the protein if the DNA codon sequence is mutated
In Normal temps, the protein has normal function.
In High temps, the protein has an altered function.
Define the Initiator protein (DnaA)
Initiator protein (DnaA) binds to the origin of replication causing local unwinding and a short stretch of single-stranded DNA.
DNA helicase
attaches at the replication fork and breaks the H-bonds that hold the DNA together
SSB (single-stranded binding proteins)
Coat single-stranded DNA to protect it, stabilize it, and prevent double-stranded DNA (hairpins)
Gyrase
a topoisomerase that relieves supercoiling ahead of replication fork
What is primase in replication?
synthesizes short RNA primers to allow DNA synthesis to begin
What is the primosome?
Helicase and primase
What makes eukaryotic and prokaryotic replication different?
Eukaryotic replication involves:
- Multiple origins of replication
- Replication of telomeres
- Linear chromosomes formed
- Nucleosome assembly follows replication
- Many different DNA polymerases
-Origin must be licensed or approved for replication to occur.
Why is replication at the end of linear chromosomes (telomeres) problematic?
DNA replication would leave gaps at the 5’ end of the strand where DNA Pol 3 can’t add anything, and the chromosome would shorten each time the cell divides
How does telomerase accomplish replication of telomeres?
Telomerase contains RNA which it uses to make several repeats of DNA to extend the 3’ end of the telomere.
How is the RNA used in a telomerase?
The RNA is used as a template for DNA synthesis (reverse transcription). After several nucleotides are added, telomerase moves along the DNA and more nucleotides are added. Eventually telomerase is removed.
