DNA Replication Flashcards
How many components do nucleotides have?
3 components
What are the components of a DNA Nucleotide?
Phosphate group, sugar and Base
How are DNA strands held together?
Anti-parallel strands are held together by hydrogen bonding
What are the three general features of DNA replication|?
-Semi Conservative
-Bidirectional
- Occurs during S phase of the cell cycle
Who suggested the self replication of DNA?
Watson and Crick
How did Watson and Crick suggest self replication of DNA occurs?
One strand is taken from the parent strand, the other is a newly synthesised strand
What did the Meselson and Stahl demonstrate?
That DNA replicated semi-conservatively
What are the two steps to semi-conservative DNA replication?
-DNA unwound to separate template strands
-Addition new nucleotides linked by covalent bonding
How is the sequence of DNA determined?
By complementary base pairing with bases on template strand
What does it mean when DNA Replication is bidirectional?
replication proceeds in both directions
During which part of the cell cycle does DNA Replication occur?
During the S phase.]
Is eukaryotic DNA synthesis similar to prokaryotic DNA synthesis?
yes, however Eukaryotic DNA synthesis is more complex
Why is DNA replication in eukaryotes more complex?
-Eukaryotic cells contain more DNA
-Chromosomes are Linear ( multiple replicons needed)
-DNA complexed with proteins (DNA packaging)
what is the rate od DNA replication in eukaryotes?
2kb/min, one chromosomes every 35 days
How tightly are nucleosomes packed?
They are tightened into 30nm fibres
What does the packaging of eukaryotic DNA depend on?
Histones
What are these histones?
positively charged proteins
What is the relationship between DNA and histones?
DNA wraps around histones to form nucleosomes
What does the phrase “beads on a string” refer to?
the beads are the tightly packed nucleosomes that are connected by linker DNA
What else does DNA replication involve?
It involves enzymes and proteins
How many proteins are involved in the replication of DNA?
7 proteins/enzymes
Which enzyme is required for the unwinding of the DNA double helix
Topoisomerase
Which enzyme is required for the separation of the DNA double helix into two strands
DNA helicase, by breaking the H bonds
How does DNA Helicase break the H bonds?
DNA Helicase uses energy from ATP to break the H bonds
Which enzyme catalyses the formation of phosphodiester bonds between nucleotides?
DNA POLYMERASE III
What does DNA Polymerase III require to elongate the DNA chain?
-DNA Template strand to copy
-RNA Primer
4 dNTPs
What is an RNA Primer?
A short piece of RNA
In which direction does the chain elongate?
5’ to 3’
What is the role of DNA Polymerase?
Catalyses the elongation of DNA chains
What does the enzyme Primase do?
Synthesises an RNA Primer
How are the two DNA strands joined together?
DNA Ligase
What is the role of DNA Polymerase I?
The RNA primer is removed and replaced with DNA
Which direction does DNA polymerase work in?
5’ to 3’
What are the 2 strands called during replication?
the leading strand and discontinuous strand
