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DNA
DNA replication
Semi-conservative
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Mary
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Cards (21)
What type of replication do scientists call DNA replication?
Semi-conservative
replication
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What happens to the DNA double helix during semi-conservative replication?
It separates into two
polynucleotide
strands
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How many molecules of DNA are produced at the end of semi-conservative replication?
Two
molecules of DNA
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What does each of the two copies of DNA contain after replication?
One
strand
from the original and one new strand
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In what decade was the structure of DNA first discovered?
1950s
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What was one possibility for how DNA replicated when it was first discovered?
Conservative replication
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What element do all bases in DNA contain?
Nitrogen
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What are the two main forms of nitrogen isotopes?
Nitrogen 14
and
nitrogen 15
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Which nitrogen isotope is more common?
Nitrogen
14
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How do nitrogen 15 atoms compare to nitrogen 14 atoms?
Nitrogen 15
atoms are slightly heavier
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What did scientists do with the bacteria to study DNA replication?
They
extracted
the DNA and
centrifuged
it
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What does the position of the DNA band in the centrifuge depend on?
How
heavy
the DNA is
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Where did the DNA band form when grown on nitrogen 14?
Near the
top
of the tube
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Where did the DNA band form when grown on nitrogen 15?
Near the
bottom
of the tube
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What happened when bacteria grown on nitrogen 15 were transferred to nitrogen 14?
The DNA produced a
band
in between the two bands
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What does the intermediate band indicate about the DNA strands?
It contains one strand of
nitrogen 14
and one of
nitrogen 15
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What happens when the bacteria replicate one more time on nitrogen 14?
It produces a bond pattern with two
bands
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How would the results differ if DNA replicated conservatively?
One molecule would contain only
nitrogen 15
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What would be the bonding pattern after two rounds of conservative replication?
One molecule with
nitrogen 15
and three with
nitrogen 14
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What are the key steps in the experiment to determine DNA replication type?
Extract DNA from bacteria.
Centrifuge
to observe band position.
Grow bacteria in
nitrogen 15
.
Transfer to
nitrogen 14
and replicate.
Analyze band positions after centrifugation.
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What are the implications of the semi-conservative replication model?
Each new DNA molecule has one
original strand
.
Ensures
genetic continuity
.
Supports the
accuracy of DNA replication
.
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