Download 11.1 Replication of DNA

11.1 Replication of
DNA
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Learning objectives:
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Describe the sequence of events in DNA
replication
Identify the enzymes and state the reactions they
control in DNA replication.
Explain the semi-conservative nature of DNA
replication
Cell division
All cells are derived from existing cells dividing.
-nuclear division : mitosis or meiosis
-cell division (cytokinesis)
Nuclear division starts with DNA replication, so
each daughter cell has all the genetic information
required to make all the enzymes and other
protein it needs.
DNA replication
Describe what you see
DNA Replication Lew port
Semi-conservative replication
Sequence
DNA helicase ………………………………..
 Double helix unwinds and the two strands …………
 Each exposed ……………… acts as a …………….
to which …………………. nucleotides are attracted
 Energy required to …………… nucleotides
 Activated nucleotides are joined by the enzyme DNA
………………
 Each new strand of DNA contains ……….the
…………..DNA molecule
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DNA movie 1, 2 ,3 KS5 Shared
Draw the DNA strands resulting from
each of these replicating.
Evidence for semi-conservative replication
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Using theories and models to explain
observations
Draw diagram to
show conservative
and semiconservative
replication
Designing an experiment to determine
which model. Meselsohn and Stahl
Key features:
- All DNA bases contain nitrogen
-nitrogen exists as lighter nitrogen 14N
and heavier isotope 15N
-bacteria incorporate nitrogen from their
growing medium into any DNA they
make
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Bacteria grown in medium containing 15N
Bacteria transferred to 14N medium for one
generation.
Centrifuge extracted DNA to separate the lighter
and heavier strands
Repeated for subsequent generations
Control Parents
14N
15N
1st generation
2nd generation
3rd generation
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What is happening?
Why are the strands
made in opposite
directions?