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CHAPTER 13 Genetic Engineering. 13-1 Changing the Living World. Selective Breeding- allowing only those animals with desired characteristics to produce the next generation ex: different dog breeds. Selective Breeding. - PowerPoint PPT Presentation
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CHAPTER 13Genetic Engineering
13-1 Changing the Living World
Selective Breeding- allowing only those animals with desired characteristics to produce the next generation
ex: different dog breeds
Selective Breeding• Selective breeding uses genetic
variation in organisms to pass desired traits onto the next generation.
Luther Burbank (1849-1926)• Created 800 varieties of plants• Disease resistant Burbank potato-
which was used in Ireland to fight potato blight
Hybridization
• Hybridization- crossing dissimilar individuals to bring together the best of both organisms• Hybrids are often stronger than either parent
• Ex: crossing disease resistance with food producing capacity
Inbreeding
• Inbreeding- continued breeding of individuals with desired characteristics• Used to maintain desired characteristics of a line
• Problems: greater chance of having two recessive alleles for a genetic defect.
• Ex: dog breeds that have joint problems and blindness
Increasing Variation
• Breeders can increase the genetic variation in a population by inducing mutations
• Example: creating bacteria that can digest oil and clean up an oil spill
• Polyploid plants- are usually stronger and larger
13-2 Manipulating DNA
The tools of molecular biology
Genetic engineering- making changes to the DNA of an organism
What is possible with genetic engineering?
Are there any ethical or moral considerations?
• DNA extraction- cells are lysed (broken) and the DNA is separated from the other cell parts
• Cutting DNA- restriction enzymes will cut DNA at a certain location• Restriction enzymes comes from bacteria that use
them to protect against foreign DNA
Restriction Enzymes create sticky ends (ends of a DNA that can bind to other DNA fragments)
• Separating DNA- done by Electrophoresis
• Electrophoresis- separating DNA fragments based on size by using electricity
• DNA is slightly negative- it will travel to a positive charge
• DNA is cut into small fragments• The DNA goes through a matrix (agarose or
acrylamide)• The smaller fragments travel faster• Ethidium bromide can be added to see the DNA
fragments with UV light
Using the DNA sequence
Reading the DNA sequence (DNA sequencing)
DNA is put into a tube with DNA polymerase
Nucleotides are added to the tube
Some of the nucleotides have a tag. If these nucleotides are added to DNA then it stops replicating.
The tag can be radioactive or a florescent dye.
• Recombinant DNA- combining DNA from different sources• Two different organisms
• Natural DNA with artificially created DNA
PCR Polymerase Chain Reaction
• PCR- process of copying a certain segment of DNA. The segment is copied many times.
• Taq polymerase- copies DNA, does not denature at high temperatures
• Primer- short segment of DNA used to begin replication
• Developed by Kary Mullis
13-3 Cell Transformation
• Transformation- a cell takes in foreign DNA. This DNA is expressed (transcribed and translated) by the cell.
Plasmid- small, circular segment of DNA
Plasmids are useful in transformation.
Transformation
• Genetic marker- something that distinguishes organisms with a certain DNA
• Antibiotic resistance is a common genetic marker
Transforming plant cells
• A bacteria can infect a plant and transfer its DNA to the plant cells.
• 1. A certain gene is put into a plasmid.• 2. The bacteria is transformed to accept the
plasmid.• 3. The bacteria infects the plant.• 4. The plant now has the inserted gene and
incorporates it into its chromosomes.
Transforming animal cells
• Animal cells can be transformed• 1. Inject DNA directly into an egg
• 2. Use a vector (virus) to transfer DNA into a cell
13-4 Applications of Genetic Engineering
• Luciferase- enzyme that allows fireflies to glow• Luciferase gene was inserted into a plant• The plant glowed
Transgenic Organisms
• Transgenic- organisms that have genes from other species
• Transgenic bacteria- produce human insulin, growth hormone, and clotting factor• Advantages: bacteria reproduce quickly and are easy
to grow
Transgenic animals
• Mice are given human genes for their immune system to study the effect of various diseases
• Livestock are given extra copies of growth genes to grow faster
• Some animals are given genes to produce certain human proteins.
• Organ donation?
Transgenic plants
• In 2000, 52% of soy and 25% of corn grown in the US was genetically modified (GM)
• Modified to produce an insecticide and resist weed-killing chemicals
• Other possible modifications: rice with extra Vitamin A
• Should we genetically modify our plants and animals?
• What are the risks or rewards?
Cloning
• Clone- an exact genetic copy of another organism
• Do clones exist naturally?
Is cloning useful?
• Why would you want to clone an animal?
• 1997, Ian Wilmut cloned a sheep, “Dolly”
• Cows, pigs, mice and other mammals have also been cloned
• 1. Cells taken from donor• 2. An egg from a second
donor has its nucleus removed
• 3. DNA from first donor is inserted into the egg of the second donor
• 4. The egg is grown and inserted into a surrogate mother
• 5. Clone is born