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