Copyright Pearson Prentice Hall Biology Biology Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-3 Cell Transformation Recombinant DNA Host Cell DNA Target gene Modified Host Cell DNA Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Transforming Bacteria What happens during cell transformation? Copyright Pearson Prentice Hall

Transforming Bacteria During transformation, a cell takes in DNA from outside the cell. The external DNA becomes a component of the cell's DNA. Copyright Pearson Prentice Hall

Transforming Bacteria 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. Copyright Pearson Prentice Hall

Transforming Bacteria The plasmid has a genetic marker—a gene that makes it possible to distinguish bacteria that carry the plasmid (and the foreign DNA) from those that don't. Copyright Pearson Prentice Hall

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 Copyright Pearson Prentice Hall

Transforming Plant Cells How can you tell if a transformation experiment has been successful? Copyright Pearson Prentice Hall

Transforming Plant Cells If transformation is successful, the recombinant DNA is integrated into one of the chromosomes of the cell. Copyright Pearson Prentice Hall

Transforming Plant Cells In nature, a bacterium exists that produces tumors in plant cells. Researchers can inactivate the tumor-producing gene found in this bacterium and insert a piece of foreign DNA into the plasmid. The recombinant plasmid can then be used to infect plant cells. Copyright Pearson Prentice Hall

Transforming Plant Cells When their cell walls are removed, plant cells in culture will sometimes take up DNA on their own. DNA can also be injected directly into some cells. Cells transformed by either procedure can be cultured to produce adult plants. Copyright Pearson Prentice Hall

Transforming Plant Cells Inside plant cell, Agrobacterium inserts part of its DNA into host cell chromosome. Agrobacterium tumefaciens Gene to be transferred Cellular DNA Recombinant plasmid The bacterium Agrobacterium tumefaciens can be used to introduce foreign DNA into plant cells. If the transformation is successful, the DNA will be integrated into one of the cell’s chromosomes. Complete plant generated from transformed cell. Plant cell colonies Transformed bacteria introduce plasmids into plant cells. Copyright Pearson Prentice Hall

Transforming Animal Cells Many egg cells are large enough that DNA can be directly injected into the nucleus. Enzymes may help to insert the foreign DNA into the chromosomes of the injected cell. DNA molecules used for transformation of animal and plant cells contain marker genes. Copyright Pearson Prentice Hall

Transforming Animal Cells DNA molecules can be constructed with two ends that will sometimes recombine with specific sequences in the host chromosome. The host gene normally found between those two sequences may be lost or replaced with a new gene. Copyright Pearson Prentice Hall

Transforming Animal Cells Recombinant DNA Recombinant DNA replaces target gene Flanking sequences match host Target gene Recombinant DNA can replace a gene in an animal’s genome. The ends of the recombinant DNA recombine with sequences in the host cell DNA. When the recombinant DNA is inserted into the target location, the host cell’s original gene is lost or knocked out of its place.  Modified Host Cell DNA Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-3 Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-3 Plasmids can be used to transform bacteria only. plant cells only. plant, animal, and bacterial cells. animal cells only. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-3 An unknowing pioneer in the concept of cell transformation was Luther Burbank. Frederick Griffith. Oswald Avery. James Watson. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-3 One reason plasmids are useful in cell transformation is that they are found in all types of cells. prevent gene replication. counteract the presence of foreign DNA. have genetic markers indicating their presence. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-3 A common method of determining whether bacteria have taken in a recombinant plasmid is to introduce them into plant cells. introduce them into animal cells. treat them with an antibiotic. mix them with other bacteria that do not have the plasmid. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 13-3 Successful transformation of an animal or a plant cell involves the integration of recombinant DNA into the cell’s chromosome. changing the cell’s chromosomes into plasmids. treating the cell with antibiotics. destroying the cell wall in advance. Copyright Pearson Prentice Hall

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