Genetic Engineering and Selective Breeding Notes

Selective Breeding: Breeding Plants and Animals for the Benefit of Humans Selective Breeding: Selecting individuals with desired traits to produce offspring for the next generation Used to produce most crops (corn, wheat…) Used to produce all breeds of domestic animals – dogs, horses, cats, sheep, cattle Also called artificial selection

developed over 800 varieties of plants. All of the different plants produced from wild mustard by selective breeding! Luther Burbank (1849-1926) developed over 800 varieties of plants.

Limits of Selective Breeding It can be a slow process, taking lots of time and many generations to get the traits that you want. Can not mix traits from two different species Can result in undesirable offspring or traits Example: Might want plants that are drought resistant; however, end up with drought resistant plants that don’t produce many seeds!

Two Types of Selective Breeding: 1. Inbreeding Inbreeding: crossing two individuals with similar traits. Advantages: Desired trait is enhanced and preserved through many generations Disadvantages: Decreases genetic variation which could lead to vulnerability to disease Homozygous recessive traits that are unwanted or unhealthy are more likely to show up.

This entire crop was wiped out in weeks by one disease! Disadvantages of Inbreeding Because of the loss of genetic variation within this crop, all were equally vulnerable to disease. This entire crop was wiped out in weeks by one disease!

Two Types of Selective Breeding: 2. Hybridization Hybridization: crossing 2 dissimilar, but related organisms Offspring called hybrids Advantages: Usually stronger/hardier than parents – known as hybrid vigor Disadvantages: May promote the loss of native species if released into the wild.

Hybridization Examples 1. African catfish (left) grows faster than Thai catfish. 2. Thai catfish (middle) has better tasting flesh than African catfish. 3. Hybrid (right) grows fast & has good tasting flesh. Problem: It has been released into rivers of Thailand and is disrupting food chains.

Other hybrids: The horse and donkey are mated to produce a mule Other hybrids: The horse and donkey are mated to produce a mule. The lion and tiger are breed to produce a Liger or Tigon. The horse and zebra are mated to produce a zorse

Genetic engineering: changing an organism’s DNA to make it more beneficial to humans

Genetic Engineering: Recombinant DNA and Transgenic Organisms Recombinant DNA: DNA made from two separate species A gene from one organism is “recombined” with another organisms DNA. Transgenic Organism: any organism that contains recombinant DNA. These new gene combinations could never be possible in nature

Researchers isolate a gene from an organism that has the trait they want to give to a plant. and cells are grown Transgenic Plants

Just for Fun?- a glowing tobacco plant

What’s Next on Your Plate? http://archives.cbc.ca/IDD-1-75-1597/science_technology/genetically_modified_food/ What’s Next on Your Plate? What genes do we want them to have? Insect, Herbicide, and Fungal resistance Drought resistance Product quality New vitamins or other nutritional benefits Longer Shelf Life (Flavr Savr Tomato)

Transgenic Organisms: Plants Example: Rice plants and daffodils can not cross pollinate with each other in nature. The rice on the right is called Golden Rice. Its genome contains the gene for producing vitamin A from daffodils. This rice is healthier for people who do not get enough vitamin A in their diets.

Transgenic Organisms: Animals Animals are now being produced with genes that increase milk production and muscle mass (meat). Problem: unhealthy; legs cannot support weight

Transgenic Organisms: Animals Genetically engineered mice used in cancer research: Contain gene from glowing jellyfish Glow when a cancer is growing in them Mice are given chemotherapy drugs; if the tumor shrinks, they glow less & less Mice don’t die from the cancer or the chemotherapy drugs Mice expressing “glow” gene from jellyfish. Glowing jellyfish http://www.pbs.org/wgbh/nova/baby/

Transgenic Organisms: Bacteria Used to produce important medicines: Insulin for diabetics Human growth hormone Anticoagulants for (for treating heart attack patients) Bacteria cultures Insulin

Other Uses for Transgenic Bacteria What’s Next? The artificial sweetener in most diet sodas phenylalanine is already being made by transgenic bacteria. How about making a transgenic bacteria that when introduced to the mouth, prevents cavities? What about transgenic bacteria able to clean up oil spills?

Dangers of Transgenic Organisms Ethical problem (should we) Transgenic bacteria could be used to create biological weapons Insertion of gene may interfere with workings of other genes causing disease A superior transgenic organism that escaped into the environment may damage the ecosystem (food chains)

Genetic Engineering and the Future Got Silk? Video Spider silk in goat’s milk

Creating hybrids to study evolutionary relationships Hybrid form is similar to types found in archeological digs. Hugh Iltis Corn domestication started around 10,000 years ago in central America. Creating hybrids between modern corn and the wild grass teosinte has produced fertilize hybrids. Analyzing the genetic differences between the hybrids and parent stocks, has shown that single gene mutations are responsible for: Changing a bushy phenotype (seen in teosinte) to a single stalk phenotype (corn) Turning teosinte seeds inside out—the hard outer casing became the central cob.