Copyright Pearson Prentice Hall Biology Biology Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-2 Manipulating DNA Copyright Pearson Prentice Hall

The Tools of Molecular Biology How do scientists make changes to DNA? Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

The Tools of Molecular Biology In genetic engineering, biologists make changes in the DNA code of a living organism. Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

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? Copyright Pearson Prentice Hall

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 Molecular biologists have developed different techniques that allow them to study and change DNA molecules. Restriction enzymes cut DNA at specific sequences. This drawing shows how restriction enzymes are used to edit DNA. The restriction enzyme EcoR I, for example, finds the sequence CTTAAG on DNA. Then, the enzyme cuts the molecule at each occurrence of CTTAAG. The cut ends are called sticky ends because they may “stick” to complementary base sequences by means of hydrogen bonds. Sticky end Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

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.  Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 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. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 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. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-2 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-2 Restriction enzymes are used to extract DNA. cut DNA. separate DNA. replicate DNA. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-2 During gel electrophoresis, the smaller the DNA fragment is, the more slowly it moves. heavier it is. more quickly it moves. darker it stains. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-2 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. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-2 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. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-2 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. Copyright Pearson Prentice Hall

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