Genetic Engineers can alter the DNA code of living organisms. Selective Breeding Recombinant DNA PCR Gel Electrophoresis Transgenic Organisms Genetic Engineering
Changing the Living World • Selective Breeding • Humans use selective breeding, which takes advantage of naturally occurring genetic variation in plants, animals, and other organisms, to pass desired traits on to the next generation of organisms. • All modern-day crops were cultivated by this method • as well as all breeds of dogs. Go to Section:
Selective breeding transformed teosinte's few fruitcases (left) into modern corn's rows of exposed kernels (right).
Teosinte – ancestor of corn (Mexico) Breeding and artificial selection • Cob selection • 5000BC – 2cm • 3000BC – 4cm • 1000AD – 13cm
Breed only those plants or animals with desirable traits People have been using selective breeding for thousands of years with farm crops and domesticated animals. Selective Breeding
Genetics and Biotechnology Selective Breeding • The process by which desired traits of certain plants and animals are selected and passed on to their future generations is called selective breeding. Saint Bernard Rescue dog Husky Sled dog German shepherd Service dog
Selective Breeding Inbreeding is the continued breeding of individuals with similar characteristics.
Inbreeding The controlled breeding of closely related organisms. Positive effects: controlled traits and characteristics. Pure bred dogs Negative effects: excessive inbreeding can produce unwanted effects because of lack of variation. Blindness in German shepherds
Inbreeding • Has risks due to the similarity of the genes between these two organisms. • There is a higher risk of defective recessive alleles pairing up in their offspring. • Ex. Blindness, deafness (white cats, dalmations) • hip dysplasia -(GoldenRetrievers)
Hybridization – The crossing of dissimilar individuals to bring together the best of both organisms.
So if inbreeding reduces variation and makes individuals very similar, how do you increase variation?
Increasing variation Use radiation or chemicals Can produce new strains of bacteria and new plants.
Increasing Variation Mutations can be induced to help create variation in organisms. Polyploidy plants have an extra chromosome.
Polyploidy Having a multiple of the normal chromosome number. Example: regular chromosome number is 9. Polyploidy condition could be 18, 27, 36, etc.
More complex forms of genetic engineering include gene splicing, transferring genetic material from one organism to another Recombinant DNA
Biotechnology A “new” field of biology that utilizes genetic engineering to produce new substances in the fields of health and industry.
Recombinant DNA • The manipulation and combination of DNA from two sources • Bacterial DNA + human gene for insulin • http://player.discoveryeducation.com/?guidAssetId=166DED13-FCC3-4388-82B7-07ED4987DDE5
Recombinant DNA The ability to combine the DNA of one organism with the DNA of another organism. Recombinant DNA technology was first used in the 1970’s with bacteria.
Recombinant Bacteria Remove bacterial DNA (plasmid). Cut the Bacterial DNA with “restriction enzymes”. Cut the DNA from another organism with “restriction enzymes”. Combine the cut pieces of DNA together with another enzyme and insert them into bacteria. Reproduce the recombinant bacteria. The foreign genes will be expressed in the bacteria.
Gene for human growth hormone Recombinant DNA Gene for human growth hormone DNA recombination Human Cell Sticky ends DNA insertion Bacterial Cell Bacterial chromosome Bacterial cell for containing gene for human growth hormone Plasmid
How recombination works • Cut plasmid (circular piece of bacteria DNA that serves as a “host”) with restriction enzyme • Cut gene of interest with restriction enzyme • Splice together gene of interest and plasmid
Cutting DNA Usually use a restriction enzyme : a chemical used to cut out a specific segment of DNA.
Cutting and Pasting Use DNA synthesizers to make recombinant DNA (DNA from two different organisms spliced together)
Sneaking In You probably have heard of computer viruses. Once inside a computer, these programs follow their original instructions and override instructions already in the host computer. Scientists use small “packages” of DNA to sneak a new gene into a cell, much as a computer virus sneaks into a computer.
1. Computer viruses enter a computer attached to some other file. What are some ways that a file can be added to a computer’s memory? A file can be downloaded from a CD or the Internet. 2. Why would a person download a virus program? The computer user would not willingly download a virus but would download a program that appeared to be useful. 3.If scientists want to get some DNA into a cell, such as a bacterial cell, to what sort of molecule might they attach the DNA? Possible answers: a useful protein or a strand of DNA that the cell would recognize and accept
Vocab Plasmid - circular DNA molecule found in bacteria genetic marker - gene that makes it possible to distinguish bacteria that carry a plasmid with foreign DNA from those that don’t Recombinant DNA – DNA that has been created artificially. DNA from two or more sources is incorporated into a single recombinant molecule.
Plasmids A small circular molecule of DNA It often has a DNA sequence that serves as an origin of replication. Contain genetic markers.
Vectors: is a DNA molecule used as a vehicle to transfer foreign genetic material into another cell Plasmids Viruses bacteriophages
Characteristics of a Vector Can replicate independently in the host cell – Has restriction sites Has a reporter gene “marker” that will announce its presence in the host cell (Anti-biotic resistance, P-Glo) Is a small size in comparison to the host chromosome for ease of isolation
pGlo Transformation of E. coli with the pGlo plasmid If the bacterium uptakes the plasmid it should glow in response to long range uv light
Transformation When a cell (usually a bacterium) takes in DNA from outside the cell and incorporates it into its own DNA. Example: Griffith’s rats
Cell Transformation • During transformation, a cell takes in DNA from outside the cell. This external DNA becomes a component of the cell’s DNA. • Transforming Bacteria • Plasmid – circular DNA molecule found in bacteria. • Why have plasmids been useful for DNA transfers? • It has a DNA sequence (gene) that helps promote plasmid replication. If the foreign DNA manages to get inside, it will get replicated (copied). • It has a genetic marker – a gene that makes it possible to distinguish whether it is carrying the foreign DNA. They usually use a gene that is resistant to antibiotics. The bacterial cell will not die when exposed to an antibiotic. When exposed, if it doesn’t die, you know the foreign DNA is inside. Section 13-3
Figure 13-9 Making Recombinant DNA Section 13-3 Gene for human growth hormone Recombinant DNA Gene for human growth hormone DNA recombination Human Cell Sticky ends DNA insertion Bacterial Cell Bacterial chromosome Bacterial cell for containing gene for human growth hormone Plasmid
B. Transforming Plant Cells Plant cells can be transformed just as easily as other cells. The bacterium Agrobacteriumtumefacienscan be used to introduce foreign DNA into plant cells. This bacterium normally enters cells and causes tumors. Scientists can inactivate the bacterium and use it as their vector. (carrier) Scientists used the firefly luciferasegene to create glowing tobacco plants!!
Applications of Genetic Engineering • 1986 – Steven Howell created the glow in the dark tobacco • This proved the basic mechanism of how genes work was true for all living organisms. • Transgenic Organisms • Transgenic - a organism which contains genes from another species. • Genetic engineering has spurred the growth of biotechnology, which is a new • industry that is changing the way we interact with the living world. • Mice with jellyfish genes. • Only glow under • florescent lights. They • passed this gene to their • offspring. 2002
Seen in ordinary light, one such pig appears yellowish. Under ultraviolet light, the pigs glow green.
Restriction Enzymes Section 13-2 Recognition sequences DNA sequence
Restriction Enzymes Section 13-2 Recognition sequences DNA sequence Restriction enzyme EcoRI cuts the DNA into fragments. Sticky end