DNA Replication Flashcards
What are the steps of Prokaryotic DNA Replication?
Complementary Strand Separation
Replication Fork Formation
Chain Elongation
RNA Primer Excision and Replacement by DNA
Proofreading of newly synthesized DNA
Termination
Prokaryotic DNA Replication: Complementary Strand Separation
What does DNA Polymerase use as a template?
ssDNA
Prokaryotic DNA Replication: Complementary Strand Separation
Ori C (origin of replication) is consensus ____ which facilitates ____
__A-T rich__
__melting__
A-T rich means that the hydrogen bonds are weaker which facilitates separation
Prokaryotic DNA Replication: Complementary Strand Separation
How many points of origin of replication in prokaryotes?
Single origin
Prokaryotic DNA Replication: Complementary Strand Separation
What are the proteins required for Initiation and Strand Separation?
DnaA
DNA helicase DnaB
Single-Stranded Binding Protein
Prokaryotic DNA Replication: Complementary Strand Separation
Function of DnaA
Binds to OriC sequences
Helps DNA melting and strand separation
Prokaryotic DNA Replication: Complementary Strand Separation
Function of DnaB
Binds to ssDNA and unwinds the double helix
Prokaryotic DNA Replication: Complementary Strand Separation
Single-Stranded Binding Protein
Binds to ssDNA to prevent reannealing
Prokaryotic DNA Replication: Complementary Strand Separation
Why may supercoils form during complementary strand separation?
Due to double helix separation
Prokaryotic DNA Replication: Complementary Strand Separation
Which enzymes help release supercoils?
DNA Topoisomerase I
DNA Topoisomerase II
Prokaryotic DNA Replication: Complementary Strand Separation
Steps of DNA Topoisomerase I action
Cuts one DNA strand allowing the other strand to pass through and relieve supercoil tension
Reseals cut after completion
Prokaryotic DNA Replication: Complementary Strand Separation
DNA Topoisomerase I ATP requirement
No ATP requirement
Prokaryotic DNA Replication: Complementary Strand Separation
Steps of DNA Topoisomerase II action
Binds tightly to DNA double helix
Makes transient breaks in both strands
Enzyme causes a second stretch of DNA double helix to pass through the break
Reseals break
Prokaryotic DNA Replication: Complementary Strand Separation
DNA Topoisomerase II ATP requirement
ATP required
Prokaryotic DNA Replication: Complementary Strand Separation
Which drugs may target topoisomerases?
Anticancer Agents (Chemotherapeutics)
Prokaryotic DNA Replication: Replication Fork Formation
The 2 strands unwind in opposite directions forming a …
replication bubble
Prokaryotic DNA Replication: Replication Fork Formation
Direction of DNA Polymerase reading
3’ → 5’
Prokaryotic DNA Replication: Replication Fork Formation
In what direction does DNA Polymerase synthesize new DNA?
5’ → 3’
Prokaryotic DNA Replication: Replication Fork Formation
Which strand is synthesized continuously
Leading Strand (3’ → 5’) towards replication fork
Prokaryotic DNA Replication: Replication Fork Formation
Which strand is synthesized non-continuously?
Lagging Strand (5’ → 3’) away from replication fork
Prokaryotic DNA Replication: Replication Fork Formation
How is the Lagging Strand synthesized?
Short fragments called Okazaki fragments interupted by RNA primers
Prokaryotic DNA Replication: Replication Fork Formation
How are Okazaki fragments linked?
After removing RNA primers, fragments are joined by ligase
Prokaryotic DNA Replication: Replication Fork Formation
What initiates DNA strand synthesis?
RNA Polymerase adds RNA primers for DNA polymerase to act on
Primers are removed after replication
Prokaryotic DNA Replication: Chain Elongation
Describe the process of chain elongation
DNA polymerase elongates DNA by adding dNTPs from the RNA primer
Prokaryotic DNA Replication: Chain Elongation
DNA polymerase III function
Chain elongation of leading and lagging strands
Prokaryotic DNA Replication: Chain Elongation
How many dNTPs (nucleotides) must be presents for elongation process?
4
Prokaryotic DNA Replication: RNA Primer Excision and Replacement by DNA
How far does the DNA polymerase III go on the lagging strand?
Until it is blocked by proximity to RNA primer
Prokaryotic DNA Replication: RNA Primer Excision and Replacement by DNA
What catalyses the replacement of the RNA primer?
DNA Polymerase I
Prokaryotic DNA Replication: RNA Primer Excision and Replacement by DNA
What catalyses the formation of the phosphodiester bonds between Okazaki Fragments?
DNA Ligase
Prokaryotic DNA Replication: Proofreading of Newly Synthesized DNA
Describe the process of proofreading DNA
DNA Polymerase has exonuclease activity in 3’ → 5’ direction
Prokaryotic DNA Replication: Termination
How is DNA replication terminated?
Binding of specific protein to replication termination sites of DNA
Where does eukaryotic DNA replication originate from?
Multiple sites along DNA helix
What is the benefit of having multiple origins of replication?
Faster replication process
DNA Replication in Eukaryotes
How are RNA primers removed in Eukaryotes?
RNAase H
DNA Replication in Eukaryotes
What are the eukaryotic DNA polymerases?
Pol α
Pol ε
Pol δ
Pol β
Pol γ
DNA Replication in Eukaryotes
Pol α function
Synthesizes short RNA segment
Extended by Pol α 5’ → 3’ polymerase activity
DNA Replication in Eukaryotes
Pol ε function
Completes DNA synthesis on leading strand
DNA Replication in Eukaryotes
Pol δ function
Elongates Okazaki Fragments of lagging strand
Use 3’→5’ exonuclease activity to proofread newly synthesized DNA
DNA Replication in Eukaryotes
Pol β function
Involved in gap filling in DNA repair
DNA Replication in Eukaryotes
Pol γ function
Replicates mitochondrial DNA
DNA Replication in Eukaryotes
Which proteins control progression through cell cycle?
Cyclins
Cyclin-Dependent Kinases (CDKs)
DNA Replication in Eukaryotes
What is an oncogene?
Altered gene which accelerates cell division
E.g. Ras and MYC oncogenes
DNA Replication in Eukaryotes
What are tumor suppressor genes?
Inhibit cell growth and division
E.g. P53 gene and RB gene
