Chapter 15 Biotechnology (Sections 15.6 - 15.10)

Chapter 15Biotechnology (Sections 15.6 - 15.10)

15.5 Genomics • Genomicsprovide insights into human genome function • Full genome sequencing is now available, but it will be a long time before we understand all the coded information • genomics • The study of genomes • Includes whole-genome comparisons, structural analysis of gene products, and the study of small-scale variation

Comparing Genomes • Comparing genomes of different organisms shows evidence of evolutionary relationships, and is used in medical research • This is a region of the gene for a DNA polymerase:

DNA Profiling • DNA profiling identifies a person by their DNA • Examples of DNA profiling include determining an individual’s array of SNPs on microscopic arrays, and analysis of short tandem repeatsusing PCR • In a criminal investigation, a short tandem repeat profile is called a DNA fingerprint

Key Terms • DNA profiling • Identifying an individual by analyzing the unique parts of his or her DNA • short tandem repeats • In chromosomal DNA, sequences of 4 or 5 bases repeated multiple times in a row

SNP: Chip Analysis of a Genome • This entire chip tests for 550,000 SNPs • Each spot is a region where the individual’s DNA has hybridized with one SNP

A Short Tandem Repeat Profile • Each peak represents one short tandem repeat – the size of a peak indicates the number of repeats at that locus

ANIMATION: Automated DNA sequencing To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

ANIMATION: DNA fingerprinting To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

ABC Video: Personalized Health Care

15.6 Genetic Engineering • Genetic engineering produces a genetically modified organism (GMO) • A gene may be altered and reinserted into an individual of the same species • A gene from one species may be transferred to another to produce an organism that is transgenic

Key Terms • genetic engineering • Process by which deliberate changes are introduced into an individual’s genome • genetically modified organism (GMO) • Organism whose genome has been modified by genetic engineering • transgenic • Refers to a genetically modified organism that carries a gene from a different species

Engineered Microorganisms • The most common GMOs are bacteria and yeast • Bacteria have been modified to produce medically important proteins such as insulin • Engineered bacteria also produce enzymes used in food manufacturing, such as chymotrypsin

A GMO • E. coli modified to produce a fluorescent protein from jellyfish

ABC Video: Picking Your Baby’s Gender; Selecting Sex Causes Controversy

15.7 Designer Plants • Genetically engineered crop plants are widespread in the US • Researchers use a Tumor-inducing (Ti) plasmid from bacteria as a vector to transfer foreign or modified genes into food crop plants such as soybeans, squash, and potatoes • Transgenic crop plants may be resistant to diseases, offer improved yields, or make a protein (Bt) toxic to insect larvae

Using the Ti Plasmid to Make a Transgenic Plant

Using the Ti Plasmid to Make a Transgenic Plant A A Ti plasmid is inserted into an Agrobacterium tumefaciens bacterium. The plasmid carries a foreign gene. B The bacterium infects a plant cell and transfers the Ti plasmid into it. The plasmid DNA becomes integrated into one of the cell’s chromosomes. C The plant cell divides, and its descendants form an embryo. E The transgenic plant expresses the foreign gene. This tobacco plant is expressing a firefly gene. D The embryo develops into a transgenic plant. Fig. 15.12, p. 229

Using the Ti Plasmid to Make a Transgenic Plant Fig. 15.12a, p. 229

Using the Ti Plasmid to Make a Transgenic Plant A A Ti plasmid is inserted into an Agrobacterium tumefaciens bacterium. The plasmid carries a foreign gene. Fig. 15.12a, p. 229

Using the Ti Plasmid to Make a Transgenic Plant Fig. 15.12b, p. 229

Using the Ti Plasmid to Make a Transgenic Plant B The bacterium infects a plant cell and transfers the Ti plasmid into it. The plasmid DNA becomes integrated into one of the cell’s chromosomes. Fig. 15.12ab, p. 229

Using the Ti Plasmid to Make a Transgenic Plant Fig. 15.12c, p. 229

Using the Ti Plasmid to Make a Transgenic Plant C The plant cell divides, and its descendants form an embryo. Fig. 15.12c, p. 229

Using the Ti Plasmid to Make a Transgenic Plant Fig. 15.12d, p. 229

Using the Ti Plasmid to Make a Transgenic Plant D The embryo develops into a transgenic plant. Fig. 15.12d, p. 229

Using the Ti Plasmid to Make a Transgenic Plant Fig. 15.12e, p. 229

Using the Ti Plasmid to Make a Transgenic Plant E The transgenic plant expresses the foreign gene. This tobacco plant is expressing a firefly gene. Fig. 15.12e, p. 229

ANIMATION: Gene transfer using a Ti plasmid To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

Genetically Modified (Bt) Corn • The Bt gene makes genetically modified corn plants insect resistant • Corn produced by unmodified plants is more vulnerable to insect pests

More GMOs • Transgenic crop plants engineered for drought tolerance and nutrition are being developed for impoverished areas • Example: Rice plants engineered to make β-carotene, a precursor of vitamin A, in their seeds • The most widely planted GMO crops include corn, sorghum, cotton, soy, canola, and alfalfa engineered for resistance to glyphosate, an herbicide

Concerns with GMOs • The engineered gene for glyphosate resistance is appearing in wild plants and in nonengineered crops, which means that transgenes can (and do) escape into the environment • Many people are opposed to any GMO crops, calling such foods “Frankenfoods” • GMO use is a controversial issue; read the research and form your own opinions

ANIMATION: Transferring genes into plants To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERE

15.8 Biotech Barnyards • Genetically modified (GM) animals are invaluable in medical research and other applications: • GM mice are used in gene research, and as models of human diseases • GM animals make proteins that treat cystic fibrosis, heart attacks, blood clotting disorders, and nerve gas exposure • GM goats produce spider silk protein in their milk • GM rabbits make human interleukin-2 • GM farm animals produce more meat or milk

Genetically Modified Animals • The pig on the left is transgenic for a yellow fluorescent protein; its nontransgenic littermate is on the right

Genetically Modified Animals • Mira the transgenic goat produces a human anticlotting factor in her milk

Genetically Engineered Animals in Research • Multiple pigments in transgenic “brainbow mice” allow researchers to map complex neural circuitry of the brain • Fluorescence micrograph shows individual nerve cells in the brainstem

Knockouts and Organ Factories • Human donors for organ transplants are in short supply, and donated organs are subject to rejection • Genetically modified animals may one day provide compatible organs and tissues for xenotransplantation into humans • xenotransplantation • Transplantation of an organ from one species into another

Key Concepts • Genetic Engineering • Genetic engineering, the directed modification of an organism’s genes, is now a routine part of research and development • Genetically modified organisms are now quite common

15.9 Safety Issues • Researchers didn’t know whether new technologies might produce superpathogens or new, dangerous forms of life • Safety guidelines minimize potential risks to researchers in genetic engineering labs • Government regulations limit release of genetically modified organisms into the environment, but don’t guarantee against accidental releases or unforeseen environmental effects

15.10 Genetically Modified Humans • With gene therapy, a gene is transferred into body cells to correct a genetic defect or treat a disease • As with any new technology, potential benefits of genetically modifying humans must be weighed against potential risks • We as a society continue to work through the ethical implications of applying new DNA technologies

Getting Better • Gene therapy is now being tested as a treatment for heart attack, sickle-cell anemia, cystic fibrosis, hemophilia A, Parkinson’s and Alzheimer’s diseases, several cancers, and inherited diseases of the eye, ear, and immune system • gene therapy • Transfer of a recombinant DNA into an individual with the goal of treating a genetic defect or disorder • Inserts an unmutated gene into an individual’s chromosomes

SCID-X1 • SCID-X1 is a severe X-linked disorder of the IL2RG gene, which codes for an immune-system receptor protein • Affected children can’t fight infections, and only survive in germ-free isolation tents • In the 1990s, 20 boys with SCID-X1 were treated with gene therapy: Researchers used a genetically engineered virus to insert unmutated copies of IL2RG into cells taken from their bone marrow – 18 were cured

Successful Gene Therapy • Rhys Evans was born with SCID–X1 • His immune system was permanently repaired by gene therapy

Getting Worse • No one can predict where a virus-injected gene will insert into a chromosome – if it interrupts a gene that controls cell division, cancer can result • Five of the 20 boys treated with gene therapy for SCID-X1 developed bone marrow cancer (leukemia), and one died • A young man with another genetic disorder had a severe allergic reaction to the viral vector – four days after gene therapy treatment, his organs shut down and he died

Getting Perfect • Using various methods to select the most desirable human traits raises ethical issues • Is it acceptable to genetically engineer cuter babies, or “superhumans” with strength or intelligence? How about to prevent obesity, aggressiveness, or homosexuality? • eugenics • Idea of deliberately improving the genetic qualities of the human race

Key Concepts • Gene Therapy • Genetic engineering continues to be tested in medical applications • It also continues to raise ethical questions

Personal DNA Testing (revisited) • Although a DNA test can reliably determine the SNPs in an individual’s genome, it can't reliably predict the effect of those SNPs on the individual • Most human traits are polygenic, and many are also influenced by environmental factors such as life-style

Chapter 15 Biotechnology (Sections 15.6 - 15.10)