6What do you think about eating genetically modified foods?
7Genetically modified organisms are called transgenic organisms. TRANSGENIC ANIMALSMice – used to study human immune systemChickens – more resistant to infectionsCows – increase milk supply and leaner meat4. Goats, sheep and pigs – produce human proteins in their milk
8Transgenic GoatThis goat contains a human gene that codes for a blood clotting agent. The blood clotting agent can be harvested in the goat’s milk.Human DNA in a goat cell
9Restriction EnzymesMolecular scissors that cut DNA at a specific nucleotide sequenceOver 200 different restriction enzymes are known, each isolated from bacteria and able to cut DNA in a unique mannerScientists use restriction enzymes in the process of genetic engineering.
11Recombinant DNAThe ability to combine the DNA of one organism with the DNA of another organism.
12Recombinant DNA Technology “Cutting and Pasting”Enzymes:Restriction enzymes = “cut”Ligase = “paste”
13Therefore, a recombinant DNA molecule contains different regions from different sources
14DNA (Gene) cloning Want to study or isolate a particular gene Need to get many copies (amplification) of the gene so it can be studied adequatelyMost organisms only have one or two copies of any gene per cell, so we need a way to amplify copies of that geneDo that via cloning into a vectorThis allows scientists to make additional copies of the gene using bacteria
15Using Plasmids Plasmid is small circle of bacterial DNA Foreign DNA can be inserted into plasmidForms recombinant plasmidsPlasmid is a cloning vectorCan deliver DNA into another cell
17Polymerase Chain Reaction (PCR) PCR allows scientists to make many copies of a piece of DNA.Heat the DNA so it “unzips”.2. Add the complementary nitrogenous bases.3. Allow DNA to cool so the complementary strands can “zip” together.
18Polymerase Chain Reaction Double-strandedDNA to copyPolymerase Chain ReactionDNA heated to90°– 94°CPrimers added tobase-pair withendsMixture cooled;base-pairing ofprimers and endsof DNA strandsDNA polymerasesassemble newDNA strandsStepped ArtFigure 16.6 Page 256
19Polymerase Chain Reaction Mixture heated again; makes all DNA fragments unwindMixture cooled; base-pairing between primers and ends of single DNA strandsDNA polymerase action again doubles number of identical DNA fragmentsStepped ArtFigure 16.6 Page 256
20Gel Electrophoresis DNA is placed at one end of a gel A current is applied to the gelDNA molecules are negatively charged and move toward positive end of gelSmaller molecules move faster than larger onesFunction- to separate DNA fragments
22What are these techniques used for? Forensic: identifying criminals & victimsIdentifying disease genes in animals & humansGene Therapy: inserting of new working copies of genes into humansAnimal knockouts: turning off of a specific gene in order to discover its function
24Engineered ProteinsBacteria can be used to grow medically valuable proteinsInsulin, interferon, blood-clotting factorsVaccines
25Engineered Plants Cotton plants that display resistance to herbicide Aspen plants that produce less lignin and more celluloseTobacco plants that produce human proteinsMustard plant cells that produce biodegradable plastic
26Cloning Dolly 1997 - A sheep cloned from an adult cell Nucleus from mammary gland cell was inserted into enucleated eggEmbryo implanted into surrogate motherSheep is genetic replica of animal from which mammary cell was taken
27The Human Genome Initiative Goal – Sequence all human DNAInitially thought by many to be a waste of resourcesSequencing was mostly completed ahead of schedule in early 2001
28Ethical IssuesWho decides what should be “corrected” through genetic engineering?Should animals be modified to provide organs for human transplants?Should humans be cloned?