BIOL1003 Lecture Notes - Lecture 15: Dna Polymerase Iii Holoenzyme, Helicase, Covalent Bond
DNA Replication
The molecular structure of DNA suggests a copying mechanism
Watson and Crick 1953
“It has not escaped our attention that the specific pairing we have postulated
immediately suggests a possible copying mechanism for the genetic material”
DNA replication in-vivo
In the S-phase of the cell cycle
oDNA is in the chromatin state
Happens at multiple positions along the DNA molecules
oReplication bubbles
Strands separate and both strands replicate at once
Bidirectional replication
Replication starts at specific sequences called origins of
replication
Semi-conservative replication
Meselson and Stahl performed an experiment:
oMitotic cells were given radioactive dNTPs
Old DNA double strand unlabelled, new one labelled
DNA molecules in daughter cells had one strand of DNA from the parent and one
that was newly synthesised
Each DNA molecule is made of an old and a new strand joined by H bonds between
the bases
DNA synthesis
Synthesis of DNA (and RNA)
Information transferred through complementary base pairing
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Document Summary
The molecular structure of dna suggests a copying mechanism. It has not escaped our attention that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material . In the s-phase of the cell cycle: dna is in the chromatin state. Happens at multiple positions along the dna molecules: replication bubbles. Strands separate and both strands replicate at once. Replication starts at specific sequences called origins of replication. Meselson and stahl performed an experiment: mitotic cells were given radioactive dntps. Old dna double strand unlabelled, new one labelled. Dna molecules in daughter cells had one strand of dna from the parent and one that was newly synthesised. Each dna molecule is made of an old and a new strand joined by h bonds between the bases. Information transferred through complementary base pairing: hydrogen bonding between base on template strand and the correct dntp selects the right base (a and t, g and c)