III Manipulating DNA

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III Manipulating DNA
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The Tools of Molecular Biology

• The Tools of Molecular Biology
• How do scientists make changes to DNA?

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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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The Tools of Molecular Biology

• In genetic engineering, biologists make changes
  in the DNA code of a living organism.

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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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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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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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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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The Tools of Molecular Biology
Power source
DNA plus restriction enzyme
Longer fragments
Shorter fragments
Mixture of DNA fragments
Gel
Gel Electrophoresis
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The Tools of Molecular Biology
DNA plus restriction enzyme

• First, restriction enzymes cut DNA into
  fragments.
• The DNA fragments are poured into wells on a gel.

Mixture of DNA fragments
Gel
Gel Electrophoresis
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The Tools of Molecular Biology
Power source

• An electric voltage is applied to the gel.
• The smaller the DNA fragment, the faster and
  farther it will move across the gel.

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The Tools of Molecular Biology
Power source
Longer fragments
Shorter fragments
Gel Electrophoresis
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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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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
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2
3
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5 etc.
DNA copies
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2
4
8
16 etc.
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Quiz
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• Restriction enzymes are used to
• extract DNA.
• cut DNA.
• separate DNA.
• replicate DNA.

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• During gel electrophoresis, the smaller the DNA
  fragment is, the
• more slowly it moves.
• heavier it is.
• more quickly it moves.
• darker it stains.

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• The DNA polymerase enzyme found in bacteria
  living in the hot springs of Yellowstone National
  Park illustrates
• genetic engineering.
• the importance of biodiversity to biotechnology.
• the polymerase chain reaction.
• selective breeding.

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• A particular restriction enzyme is used to
• cut up DNA in random locations.
• cut DNA at a specific nucleotide sequence.
• extract DNA from cells.
• separate negatively charged DNA molecules.

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• During gel electrophoresis, DNA fragments become
  separated because
• multiple copies of DNA are made.
• recombinant DNA is formed.
• DNA molecules are negatively charged.
• smaller DNA molecules move faster than larger
  fragments.

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END OF SECTION