13-1 Changing the Living World Photo credit: ©Anup Shah/Dembinsky Photo Associates Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Selective Breeding Selective Breeding _________________________________allows only those organisms with desired characteristics to produce the next generation. Nearly all domestic animals and most crop plants have been produced by selective breeding. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Selective Breeding Humans use selective breeding to pass desired traits on to the next generation of organisms. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Selective Breeding Hybridization  ________________________________ is the crossing of dissimilar individuals to bring together the best of both organisms. Hybrids, the individuals produced by such crosses, are often hardier than either of the parents. = + Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Selective Breeding Inbreeding  _____________________________is the continued breeding of individuals with similar characteristics. Inbreeding helps to ensure that the characteristics that make each breed unique will be preserved. Serious genetic problems can result from excessive inbreeding. Copyright Pearson Prentice Hall

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Copyright Pearson Prentice Hall Increasing Variation Breeders increase the genetic variation in a population by inducing mutations. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Increasing Variation Mutations occur spontaneously, but breeders can increase the mutation rate by using______________ _________________________. Breeders can often produce a few mutants with desirable characteristics that are not found in the original population. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Increasing Variation Producing New Kinds of Bacteria Introducing mutations has allowed scientists to develop hundreds of useful bacterial strains, including bacteria that can clean up oil spills. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Increasing Variation Producing New Kinds of Plants Mutations in some plant cells produce cells that have double or triple the normal number of chromosomes. This condition, known as polyploidy, produces new species of plants that are often larger and stronger than their diploid relatives. Polyploidy in animals is usually fatal. Except in the case of the Red Viscacha Rat Copyright Pearson Prentice Hall

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

The Tools of Molecular Biology Scientists use their knowledge of the structure of DNA and its chemical properties to study and change DNA molecules. 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_______________________, 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. Copyright Pearson Prentice Hall

The Tools of Molecular Biology Each ________________________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 A restriction enzyme will cut a DNA sequence only if it matches the sequence precisely. Recognition sequences DNA sequence Restriction enzyme EcoR I cuts the DNA into fragments Sticky end Copyright Pearson Prentice Hall

The Tools of Molecular Biology Separating DNA   In___________________________, DNA fragments are placed at one end of a porous gel, and an electric voltage is applied to the gel. When the power is turned on, the negatively-charged DNA molecules move toward the positive end of the gel. Whoa! We did this!!!!!! Copyright Pearson Prentice Hall

The Tools of Molecular Biology Gel electrophoresis can be used to compare the genomes of different organisms or different individuals. It can also be used to locate and identify one particular gene in an individual's genome. 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. This moves the DNA fragments across 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.  Gel Electrophoresis Copyright Pearson Prentice Hall

The Tools of Molecular Biology 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. 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 Using the DNA Sequence Knowing the sequence of an organism’s DNA allows researchers to study specific genes, to compare them with the genes of other organisms, and to try to discover the functions of different genes and gene combinations. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence Reading the Sequence In DNA sequencing, a complementary DNA strand is made using a small proportion of fluorescently labeled nucleotides. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence DNA strand with unknown base sequence DNA Sequencing Dye molecules DNA fragments synthesized using unknown strand as a template Knowing the sequence of an organism’s DNA allows researchers to study specific genes. In DNA sequencing, a complementary DNA strand is made using a small proportion of fluorescently labeled nucleotides. Each time a labeled nucleotide is added, it stops the process of replication, producing a short color-coded DNA fragment. When the mixture of fragments is separated on a gel, the DNA sequence can be read directly from the gel. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence Each time a labeled nucleotide is added, it stops the process of replication, producing a short color-coded DNA fragment. When the mixture of fragments is separated on a gel, the DNA sequence can be read. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence Base sequence as “read” from the order of the dye bands on the gel from bottom to top: T G C A C Knowing the sequence of an organism’s DNA allows researchers to study specific genes. In DNA sequencing, a complementary DNA strand is made using a small proportion of fluorescently labeled nucleotides. Each time a labeled nucleotide is added, it stops the process of replication, producing a short color-coded DNA fragment. When the mixture of fragments is separated on a gel, the DNA sequence can be read directly from the gel. Electrophoresis gel Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence Cutting and Pasting  Short sequences of DNA can be assembled using DNA synthesizers. “Synthetic” sequences can be joined to “natural” sequences using enzymes that splice DNA together. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence These enzymes also make it possible to take a gene from one organism and attach it to the DNA of another organism. Such DNA molecules are sometimes called recombinant DNA. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence Making Copies  ________________________________________ is a technique that allows biologists to make copies of genes. A biologist adds short pieces of DNA that are complementary to portions of the sequence. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Using the DNA Sequence DNA is heated to separate its two strands, then cooled to allow the primers to bind to single-stranded DNA. DNA polymerase starts making copies of the region between the primers. PCR song: http://www.youtube.com/watch?v=7uafUVNkuzg DNA Song: http://www.youtube.com/watch?v=-bF2QalUj1Y 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