CHAPTER 12 DNA Technology and the Human Genome Modules 12.1 – 12.6

DNA technology has many useful applications The Human Genome Project The production of vaccines, cancer drugs, and pesticides Engineered bacteria that can clean up toxic wastes

Recombinant DNA Technology a set of techniques for combining genes from different sources into a single DNA molecule producing recombinant DNA. An organism that carries recombinant DNA is called a genetically modified (GM) organism. Recombinant DNA technology is applied in the field of biotechnology. Biotechnology uses various organisms to perform practical tasks. Plasmids are key tools for DNA technology Researchers use plasmids to insert genes into bacteria

1 2 3 4 5 Cell containing gene of interest Bacterium Plasmid isolated DNA isolated 3 Gene inserted into plasmid Bacterial chromosome Plasmid Gene of interest Recombinant DNA (plasmid) DNA 4 Plasmid put into bacterial cell Recombinant bacterium 5 Cell multiplies with gene of interest Copies of gene Copies of protein Gene for pest resistance inserted into plants Clones of cell Protein used to make snow form at higher temperature Gene used to alter bacteria for cleaning up toxic waste Protein used to dissolve blood clots in heart attack therapy Figure 12.3

From Humulin to Genetically Modified Foods By transferring the gene for a desired protein product into a bacterium, proteins can be produced in large quantities.

Making Humulin In 1982, the world’s first genetically engineered pharmaceutical product was produced. Humulin, human insulin, was produced by genetically modified bacteria. Humulin was the first recombinant DNA drug approved by the FDA. DNA technology is also helping medical researchers develop vaccines.

12.16 Connection: Recombinant cells and organisms can mass-produce gene products Recombinant cells and organisms are used to manufacture useful proteins Table 12.16

Human Gene Therapy Human gene therapy is a recombinant DNA procedure that seeks to treat disease by altering the genes of the afflicted person. The mutant version of a gene is replaced or supplemented with a properly functioning one.

Figure 12.23

Treating Severe Combined Immunodeficiency SCID is a fatal inherited disease caused by a single defective gene. The gene prevents the development of the immune system. SCID patients quickly die unless treated with a bone marrow transplant. Since the year 2000, Gene therapy has successfully cured 22 children with inborn SCID. Unfortunately, three of the children developed leukemia and one of them died.

New genetic varieties of animals and plants are being produced 12.18 Connection: Genetically modified organisms are transforming agriculture New genetic varieties of animals and plants are being produced A plant with a new trait can be created using the Ti plasmid

Agrobacterium tumefaciens DNA containing gene for desired trait Plant cell 1 2 3 Ti plasmid Recombinant Ti plasmid Insertion of gene into plasmid using restriction enzyme and DNA ligase Introduction into plant cells in culture Regeneration of plant T DNA T DNA carrying new gene within plant chromosome Plant with new trait Restriction site Figure 12.18A

“Golden rice” has been genetically modified to contain beta-carotene This rice could help prevent vitamin A deficiency Figure 12.18B

Recombinant DNA Techniques Recombinant DNA techniques can help biologists produce large quantities of a desired protein. Bacteria are the workhorses of modern biotechnology. To work with genes in the laboratory, biologists often use bacterial plasmids. Plasmids are small, circular DNA molecules that are separate from the much larger bacterial chromosome.

Figure 12.7

Plasmids can easily incorporate foreign DNA. Plasmids are readily taken up by bacterial cells. Plasmids then act as vectors, DNA carriers that move genes from one cell to another.

A Closer Look: Cutting and Pasting DNA with Restriction Enzymes Recombinant DNA is produced by combining two ingredients: A bacterial plasmid The gene of interest To combine these ingredients, a piece of DNA must be spliced into a plasmid. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

Figure 12.9

This splicing process can be accomplished using restriction enzymes. These enzymes cut DNA at specific nucleotide sequences. These cuts produce pieces of DNA called restriction fragments That may have “sticky ends” that are important for joining DNA from different sources. DNA ligase pastes the DNA fragments together The result is recombinant DNA

12.5 Genes can be cloned in recombinant plasmids: A closer look Bacteria take the recombinant plasmids and reproduce This clones the plasmids and the genes they carry Products of the gene can then be harvested

Bacterial clone carrying many copies of the human gene 1 Isolate DNA from two sources Human cell E. coli 2 Cut both DNAs with the same restriction enzyme Plasmid DNA Gene V Sticky ends 3 Mix the DNAs; they join by base-pairing 4 Add DNA ligase to bond the DNA covalently Recombinant DNA plasmid Gene V 5 Put plasmid into bacterium by transformation 6 Clone the bacterium Bacterial clone carrying many copies of the human gene Figure 12.5

DNA Fingerprinting and Forensic Science DNA technology has rapidly revolutionized the field of forensics. Forensics is the scientific analysis of evidence from crime scenes. DNA fingerprinting can be used to determine whether or not two samples of genetic material are from a particular individual.

Murder, Paternity, and Ancient DNA DNA fingerprinting Has become a standard criminology tool. Has been used to identify victims of the September 11, 2001, World Trade Center attack. Can be used in paternity cases. DNA fingerprinting is also used in evolutionary research To study ancient pieces of DNA, such as that of Cheddar Man.

Figure 12.12

12.10 Gel electrophoresis sorts DNA molecules by size Restriction fragments of DNA can be sorted by size Mixture of DNA molecules of different sizes Longer molecules Power source Gel Shorter molecules Glass plates Completed gel Figure 12.10

The DNA fragments are visualized as “bands” on the gel. The bands of different DNA samples can then be compared.

Figure 12.17

One common application of gel electrophoresis is RFLP analysis Restriction fragment analysis is a powerful method that detects differences in DNA sequences The DNA molecules to be compared are exposed to a series of restriction enzymes. Scientists can compare DNA sequences of different individuals based on the size of the fragments

Figure 12.18

The Human Genome Project involves: 12.14 Connection: The Human Genome Project is unlocking the secrets of our genes The Human Genome Project involves: genetic and physical mapping of chromosomes DNA sequencing comparison of human genes with those of other species Figure 12.14

RISKS AND ETHICAL QUESTIONS 12.20 Connection: Could GM organisms harm human health or the environment? Genetic engineering involves some risks Possible ecological damage from pollen transfer between GM and wild crops Pollen from a transgenic variety of corn that contains a pesticide may stunt or kill monarch caterpillars Figure 12.20A, B

12.21 Connection: DNA technology raises important ethical questions Our new genetic knowledge will affect our lives in many ways The deciphering of the human genome, in particular, raises profound ethical issues Many scientists have counseled that we must use the information wisely Figure 12.21A-C