BIOL 1030H Lecture Notes - Lecture 10: Proofreading, Dna Ligase, Helicase
DNA must be duplicated to divide into 2 daughter cells
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DNA Replication
Double helix
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Base pairs:
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Adenine and Thymine form 2 hydrogen bonds
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Guanine and Cytosine form 3 hydrogen bons
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Alternating sugar phosphate base back bone
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Bases pair in the middle
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DNA
During replication, the two strands of the parental duplex separate
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Each parental strand serves as a template for the synthesis of a new daughter strand, using
the base-pairing rules of A with T and G with C
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This way parental strand much replicate an identical strand
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DNA Replication
Semiconservative
1.
New strand is formed by one parental and one new
Conservative
2.
Entirely new double helix
2 Hypothetical models for replication:
Strands are labeled with heavy nitrogen. The moleules form a band with the density of heavy
DNA
1.
After one round of replication in the absensce of heavy nitrogen, the parental strand still
contains the heavy nitrogen but the daughter strand contains light nitrogen. The daughter
DNA molecule form a band with an intermediate density
2.
After two rounds of replication, half of the duplex DNA molecule have one strand with heavy
and one with lighter nitrogen. The other half have both lighter nitrogen. The daughter
molecule therefore forms two bands, one intermediate in density and the other light
3.
Bacterial DNA Replication
Proves semi-conservative model
Eukaryotic DNA Replication
After two rounds of DNA replication in a labeled medium, one daughter molecule is half labeled, and
the other is fully labelled
-- semi conservatively as well
Direction of chain growth always occurs 5' to 3' and new bases are always added onto the
hydroxyl group end
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Highly conserved amongst species
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Synthesize a new strand from the original strand
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Can correct base pairings
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DNA polymerase- highly conserved amongst species- originated early one
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Replication Occurs 5' to 3'
Elongation can only occur 5' to 3'
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Daughter strand on the bottom elongates left to right, bottom strand elongates right to left
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Continous/Discointinous Replication
DNA polymerase requires a certain amount of DNA or RNA to start from
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RNA Primers
DNA Replication
April 6, 2018
2:36 PM
Biology 1030 Page 1
Document Summary
Dna must be duplicated to divide into 2 daughter cells. During replication, the two strands of the parental duplex separate. Each parental strand serves as a template for the synthesis of a new daughter strand, using the base-pairing rules of a with t and g with c. This way parental strand much replicate an identical strand. New strand is formed by one parental and one new. The moleules form a band with the density of heavy. After one round of replication in the absensce of heavy nitrogen, the parental strand still contains the heavy nitrogen but the daughter strand contains light nitrogen. Dna molecule form a band with an intermediate density. After two rounds of replication, half of the duplex dna molecule have one strand with heavy and one with lighter nitrogen. The daughter molecule therefore forms two bands, one intermediate in density and the other light.