Biology
Biology
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13-2 Manipulating DNA
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13-2 Manipulating DNA
The Tools of Molecular Biology
The Tools of Molecular Biology
How do scientists make changes to DNA?
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13-2 Manipulating DNA
The Tools of Molecular Biology
Scientists use different techniques to:
• extract DNA from cells
• cut DNA into smaller pieces
• identify the sequence of bases in a DNA molecule
• make unlimited copies of DNA
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13-2 Manipulating DNA
The Tools of Molecular Biology
In genetic engineering, biologists make changes
in the DNA code of a living organism.
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13-2 Manipulating DNA
The Tools of Molecular Biology
DNA Extraction
DNA can be extracted from most cells by a simple
chemical procedure.
The cells are opened and the DNA is separated
from the other cell parts.
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13-2 Manipulating DNA
The Tools of Molecular Biology
Cutting DNA
Most DNA molecules are too large to be analyzed,
so biologists cut them into smaller fragments using
restriction enzymes.
Which type of molecule is an enzyme?
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13-2 Manipulating DNA
The Tools of Molecular Biology
Each restriction enzyme cuts DNA at a specific
sequence of nucleotides.
Recognition sequences
DNA sequence
Restriction enzyme EcoR I cuts
the DNA into fragments
Sticky end
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13-2 Manipulating DNA
The Tools of Molecular Biology
Separating DNA
In gel electrophoresis, DNA fragments are placed
at one end of a porous gel, and an electric voltage
is applied to the gel.
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13-2 Manipulating DNA
The Tools of Molecular Biology
Power
source
DNA plus restriction
enzyme
Longer
fragments
Mixture of
DNA
fragments
Gel
Gel Electrophoresis
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Shorter
fragments
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13-2 Manipulating DNA
First, restriction
enzymes cut DNA into
fragments.
The Tools of Molecular Biology
DNA plus
restriction enzyme
The DNA fragments
are poured into wells
on a gel.
Mixture of DNA
fragments
Gel Electrophoresis
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Gel
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13-2 Manipulating DNA
The Tools of Molecular Biology
An electric voltage is
applied to the gel.
Power
source
The smaller the DNA
fragment, the faster
and farther it will
move across the gel.
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13-2 Manipulating DNA
The Tools of Molecular Biology
Power
source
Longer
fragments
Shorter
fragments
Gel Electrophoresis
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13-2 Manipulating DNA
Using the DNA Sequence
Making Copies
Polymerase chain reaction (PCR) is a technique
that allows biologists to make copies of genes.
Small amounts of DNA can be multiplied making it
easier to analyze.
Made possible by an enzyme found in a bacterium
living in hot springs in Yellow Stone National Park.
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13-2 Manipulating DNA
Using the DNA Sequence
Polymerase Chain Reaction (PCR)
DNA heated to
separate strands
DNA polymerase adds
complementary strand
DNA fragment
to be copied
PCR cycles 1
DNA copies 1
2
2
3
4
4
8
5 etc.
16 etc.
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13-2
Click to Launch:
Continue to:
- or -
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13-2
Restriction enzymes are used to
a. extract DNA.
b. cut DNA.
c. separate DNA.
d. replicate DNA.
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13-2
During gel electrophoresis, the smaller the DNA
fragment is, the
a. more slowly it moves.
b. heavier it is.
c. more quickly it moves.
d. darker it stains.
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13-2
The DNA polymerase enzyme found in bacteria
living in the hot springs of Yellowstone National
Park illustrates
a. genetic engineering.
b. the importance of biodiversity to
biotechnology.
c. the polymerase chain reaction.
d. selective breeding.
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13-2
A particular restriction enzyme is used to
a. cut up DNA in random locations.
b. cut DNA at a specific nucleotide sequence.
c. extract DNA from cells.
d. separate negatively charged DNA
molecules.
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13-2
During gel electrophoresis, DNA fragments
become separated because
a. multiple copies of DNA are made.
b. recombinant DNA is formed.
c. DNA molecules are negatively charged.
d. smaller DNA molecules move faster than
larger fragments.
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