temporary break to allow uncoiling
DESCRIPTION
Two new strands forming DNA Replication Free nucleotides with their corresponding bases are matched up against the template strand following the base pairing rule: Two new strands forming A pairs with T G C Template strand Template strandTRANSCRIPT
DNA Replication
DNA is replicated to produce an exact copy of a chromosome in preparation for cell division.
The first step requires uncoiling the DNA
Replication fork
Temporary break to allow uncoiling
Single-armed chromosomeas found in non-dividing cell
DNA Replication Free nucleotides with their corresponding bases are matched up against the template strand following the base pairing rule:
A pairs with T
T pairs with A
G pairs with C
C pairs with GTemplate
strand
Template strand
Two new strands forming
The Leading StrandEnzymes can build strandsonly in the 5’ to 3’ direction
This means that only one strand, called the leading strand, can be synthesized as a continuous strand.
Swivel point
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DNA polymerase
The parental strand provides a 'template' for synthesis of the new strand
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5'
3'5'
5'
3'
Replicationfork
Helicase: Splits and unwinds the two-stranded DNA molecule.
1
The leading strand is synthesized continuously in the 5' to 3' direction by DNA polymerase.
2
The Lagging StrandThe other complementary strand, called the lagging strand, must be constructed in fragments, which are later joined together.
3'
New complementary strand is synthesized discontinuously
5'
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3'
RNA primer
Direction of synthesis
5'
RNA polymerase:Makes a short RNA primer which is later removed.
2
DNA polymerase: Extends RNA primer with short lengths of complementary DNA to make Okazaki fragments.
3
Helicase: Splits and unwinds the two-stranded DNA molecule.
1
Enzyme Control of Replication
Direction of
synthesis
The lagging strand is formed in fragments (called Okazaki fragments) which are later joined together.
3'
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3'5'
5'3'
DNA ligase: Joins neighboring fragments together into longer strands.
4
DNA Replication
The two new strands of DNA coil up into a helix.
The double strands of DNA
coil up into a helix
DNA replication is controlled by enzymes at key stages:
Control of DNA Replication5' 3'
3'5'
Double strand of original (parental) DNA
Helicase
DNA polymerase
DNA polymerase I
DNA ligase
Direction of
synthesis
5'
3'
Replicationfork
DNA polymerase
Leading strand
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Directi
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