Module 32 Flashcards
DNA Replication
What is NDA made up of
Nucleotides
3 Key features of DNA
- Store genetic info
- Direct synthesis of other macros
- Transmits genetic information from one DNA molecule to another
DNA Replicatoion
a process where DNA is able to specify exact copies of itself
Purine Bases
A and G
Pyrimidine Bases
T and C
Antiparallel
How the DNA strands run in relation of each other
5’->3’
3’<-5’
Replication Fork
The site where parental DNA strands unwind and separate
Semiconservative replication
Each DNA consists of one parental strand and one newly synthesized daughter strand
Conservative Replication
Proposes that DNA molecules remain intact and daughter cells are completely new
Who tested the way in which DNA replicates
Meselson and Stahl
How does base pairing ensure that parental strand and daughter strand have exactly the same DNA
Complimentary base pairing of the DNA molecule and their antiparallel structure.
Mechanisms by which DNA replicates
Opening of the double helix
Separation and unwinding of the DNA strands at the replication fork
Where does DNA replication begin at
the Replication Fork
Helicase
The enzyme that separates the parental strands
Breaks hydrogen bonds between nucleotides
Single-stranded binding protiens
Bind to separate regions of the DNA molecule to prevent them from coming back together
Topoisomerase
Release the stress of the unwinding DNA molecule before it gets to the replication fork
Works upstream from the replication fork
What doe the family of topoisomerase enzymes do
Winds, unwinds, or helps relieve stress that occurs during replication and transcription
DNA Polymerase
Highly conserved, since they carry out essential functions
Replicates DNA
Properties of DNA polymerase
- It can only attach one nucleotide to another at one time
- It can only elongate one end of the DNA - It can only add nucleotides to the 3’ end of the strand
Primer
A starter for DNA synthesis
A short stretch of RNA
What must each new strand of DNA begin with
Primer
A short stretch of RNA
RNA primase
The enzyme that makes DNA primer
Where is the Hydroxyl group on RNA primers
On the 3’ carbon
OH-
Where is the phosphate on RNA primers
On the 5’ carbon
When does DNA synthesis occur
When the 3’ OH- group attacks the phosphate group of the incoming nucleotide (It’s trisphosphate)
5’–>3’ direction
Polymerization
DNA synthesis
When the 3’ OH- group attacks the phosphate group of the incoming nucleotide (It’s trisphosphate)
In what direction does polarization occur
5’–>3’ direction
Where does the energy required for the polymerization reaction come from
When the OH- group of RNA attacks the phosphate group of the nucleotide, the two other phosphates are released in the process
The high-energy PHOSPHATE BOND IS BROKEN
Leading Strand
The daughter strand that can be synthesized in one continuous polymer
Has its 3’ end pointing towards the replication site
Lagging Strand
Has multiple pieces that reach each other
3’ end points way from the replication site
Okazaki Fragments
Result of lagging strand / 3’ being away from the replication fork
Short, discontinuous. pieces of DNA
DNA replication process
DNA is unwinded at the Replication Fork
RNA Primer is laid
Synthesis of new strand at 3’
Reason for Okazaki Fragments
Without them, the DNA would have to unzip all the way before synthesis, posing the risk that the DNA parental strand folds in on itself
What do leading and lagging strands share
They are complementary to each other and their parental strand
What do all DNA strands have at their 5’ end
RNA primers
When is the RNA primer removed
When a growing fragment comes into contact with the primer of the earlier fragment
What removes a RNA primer
A different DNA polymerase
It also extends the growing fragment to fill in the space of the removal
DNA ligase
Joins all the adjacent gradients of the new DNA
What is the reason behind leading and lagging strands
DNA’s anti-parallel nature
Why is it important DNA replication occurs accurately
Mutations can occur
Proofreading
Most DNA polymerases are able to do this
DNA polymerase can immediately correct its own errors during DNA synthesis
Detects mispairing between the template and most recently added nucleotide; removes it; and corrects it
What holds new nucleotides in place
Hydrogen bonds between new pairs
Importance of mutations
They allow populations of organisms to change through time and adapt to their environment
