1. Genetic Engineering
How do scientists make changes to DNA?

2. 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
In genetic engineering, biologists make changes in the DNA code of a living organism.
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3. 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.
Cutting DNA 
Most DNA molecules are too large to be analyzed, so biologists cut them into smaller fragments using restriction enzymes.
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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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5. The Tools of Molecular Biology
DNA plus restriction enzyme
Power source
Longer fragments
Shorter fragments
Mixture of DNA fragments
Gel
Gel electrophoresis is used to separate DNA fragments. First, restriction enzymes cut DNA into fragments. The DNA fragments are then poured into wells on a gel, which is similar to a thick piece of gelatin. An electric voltage moves the DNA fragments across the gel. Because longer fragments of DNA move through the gel more slowly, they do not migrate as far across the gel as shorter fragments of DNA. Based on size, the DNA fragments make a pattern of bands on the gel. These bands can then be compared with other samples of DNA. 
Gel Electrophoresis
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6. The Tools of Molecular Biology
First, restriction enzymes cut DNA into fragments.
The DNA fragments are poured into wells on a gel.
DNA plus restriction enzyme
Gel electrophoresis is used to separate DNA fragments. First, restriction enzymes cut DNA into fragments. The DNA fragments are then poured into wells on a gel, which is similar to a thick piece of gelatin. An electric voltage moves the DNA fragments across the gel. Because longer fragments of DNA move through the gel more slowly, they do not migrate as far across the gel as shorter fragments of DNA. Based on size, the DNA fragments make a pattern of bands on the gel. These bands can then be compared with other samples of DNA. 
Mixture of DNA fragments
Gel
Gel Electrophoresis
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7. The Tools of Molecular Biology
An electric voltage is applied to the gel.
The smaller the DNA fragment, the faster and farther it will move across the gel.
Power source
Gel electrophoresis is used to separate DNA fragments. First, restriction enzymes cut DNA into fragments. The DNA fragments are then poured into wells on a gel, which is similar to a thick piece of gelatin. An electric voltage moves the DNA fragments across the gel. Because longer fragments of DNA move through the gel more slowly, they do not migrate as far across the gel as shorter fragments of DNA. Based on size, the DNA fragments make a pattern of bands on the gel. These bands can then be compared with other samples of DNA. 
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8. The Tools of Molecular Biology
Power source
Longer fragments
Shorter fragments
Gel electrophoresis is used to separate DNA fragments. First, restriction enzymes cut DNA into fragments. The DNA fragments are then poured into wells on a gel, which is similar to a thick piece of gelatin. An electric voltage moves the DNA fragments across the gel. Because longer fragments of DNA move through the gel more slowly, they do not migrate as far across the gel as shorter fragments of DNA. Based on size, the DNA fragments make a pattern of bands on the gel. These bands can then be compared with other samples of DNA. 
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
Polymerase chain reaction (PCR) is used to make multiple copies of genes.
PCR cycles 1 2 3 4
5 etc.
DNA copies 1 2 4 8
16 etc.
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13-3 Cell Transformation
Recombinant DNA
Host Cell DNA
Target gene
Modified Host Cell DNA
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12. Transforming Bacteria
During transformation, a cell takes in DNA from outside the cell. The external DNA becomes a component of the cell's DNA.
-Foreign DNA is first joined to a small, circular DNA molecule known as a plasmid.
Plasmids are found naturally in some bacteria and have been very useful for DNA transfer.
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13. Transforming Bacteria
Gene for human growth hormone
Recombinant DNA
Gene for human growth hormone
DNA recombination
Human Cell
Bacterial chromosome
Sticky ends
DNA insertion
Bacteria cell
During transformation, a cell incorporates DNA from outside the cell into its own DNA. One way to use bacteria to produce human growth hormone is to insert a human gene into bacterial DNA. The new combination of genes is then returned to a bacterial cell. The bacterial cell containing the gene replicates over and over.
Bacteria cell containing gene for human growth hormone
Plasmid
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Transgenic Organisms
Transgenic Organisms
An organism described as transgenic, contains genes from other species.
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Transgenic Organisms
Transgenic Microorganisms
Transgenic bacteria produce important substances useful for health and industry. Transgenic bacteria have been used to produce:
insulin
growth hormone
clotting factor
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Transgenic Organisms
Transgenic Animals
Transgenic animals have been used to study genes and to improve the food supply.
Mice have been produced with human genes that make their immune systems act similarly to those of humans. This allows scientists to study the effects of diseases on the human immune system.
Researchers are trying to produce transgenic chickens that will be resistant to the bacterial infections that can cause food poisoning.
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Transgenic Organisms
Transgenic Plants 
Transgenic plants are now an important part of our food supply.
Many of these plants contain a gene that produces a natural insecticide, so plants don’t have to be sprayed with pesticides.
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Cloning
Cloning Dolly
In early 1997, Dolly made headlines as the first clone of an adult mammal. 
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Cloning
Cloning Dolly
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Cloning
Cloning Dolly
In early 1997, Dolly made headlines as the first clone of an adult mammal. 
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Cloning
Cloning Dolly
In early 1997, Dolly made headlines as the first clone of an adult mammal. 
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22. Copyright Pearson Prentice Hall
Cloning
Cloning Dolly
In early 1997, Dolly made headlines as the first clone of an adult mammal. 
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23. Copyright Pearson Prentice Hall
Cloning
Cloning Dolly
In early 1997, Dolly made headlines as the first clone of an adult mammal. 
Copyright Pearson Prentice Hall

24. Copyright Pearson Prentice Hall
Cloning
Cloning Dolly
In early 1997, Dolly made headlines as the first clone of an adult mammal. 
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Cloning
Researchers hope cloning will enable them to make copies of transgenic animals and help save endangered species.
Studies suggest that cloned animals may suffer from a number of genetic defects and health problems.
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