Chapter 13 Genetic Engineering
Selective Breeding Passing on desired characteristics to the next generation. Examples: different breeds of domestic and farm animals, different varieties of plants (corn, soybeans, potatoes, apples, etc.)
Inbreeding vs. Hybridization Hybridization crossing unlike individuals to get the best of both organisms. Inbreeding crossing organisms of similar characteristics to maintain those characteristics.
Inbreeding increases the chances of two recessive alleles for a genetic defect being passed on. This has led to joint problems and blindness in German shepherds and golden retrievers.
Increasing Variation Breeders induce or cause mutations to create genetic variability. What are mutations? Inheritable changes in DNA. Breeders use radiation and chemicals to induce mutations.
Increasing Variation Breeders can increase genetic variation in a population by inducing mutations. This creates genetic variability. A mutation is a change in DNA that can be passed on to offspring. The mutation rate is sped up by using chemicals and/or radiation.
This technique has worked well with bacteria because millions of organisms can be treated at once. This has led to hundreds of useful strains of bacteria.
Enzyme Name GE Organism Use (examples) alpha-amylase bacteria converts starch to simple sugars catalase fungi reduces food deterioration, particularly egg-based products chymosin bacteria/fungi clots milk protein to make cheese cyclodextrin-glucosyl transferase bacteria starch/sugar modification Isomerase bacteria converts glucose sugar to fructose sugar glucose oxidase fungi reduces food deterioration, particularly egg-based products xylanase (hemicellulase) bacteria/fungi enhances rising of bread dough
Another method of genetic engineering is forced polyploidy. Scientists use drugs that prevent chromosomal separation to increase the normal number of chromosomes. In animals, this is usually fatal, but many plants benefit from this and produce larger crops.
13-2 Manipulating DNA DNA Extracting cell is opened and the DNA is separated from the other cell parts. Cutting DNA restriction enzymes are used like scissors to cut the DNA at specific nucleotide sequences. Each restriction enzyme looks for a unique sequence. Separating DNA gel electrophoresis is used to separate DNA fragments based on their charge and size.
What do you do with the DNA now? Scientists attach dye to the nitrogenous bases. When the base is used in replication, it terminates the strand. Then the dye-tagged fragments are separated using gel electrophoresis. Using this method, researchers can determine DNA sequences and study an organisms genes.
When researchers study genes, they often need to make copies to speed up the process. This is done using polymerase chain reaction or PCR. DNA is heated to cause the strands to separate, then cooled to allow replication to take place. This is done multiple times to make thousands or millions of copies of a gene. (Each time you double the number.)
13-3 Cell Transformation During cell transformation, a cell incorporates DNA from outside the cell into its own DNA. A common example of this is Genetically engineered bacteria. Draw diagram on the board.
13-4 Applications Transgenic Organisms organisms containing genes from another species. Examples: bacteria that contain genes for Human Growth Hormone, insulin, clotting factor, etc. Transgenic animals that grow faster and leaner, and plants that are disease resistant and produce higher yields.
Cloning 1997 Ian Wilmut successfully cloned a sheep named Dolly. Since then, cows, pigs, and mice have been cloned using similar techniques. Cloned animals have a record of suffering from genetic defects and health problems.
Restriction Enzymes 1. Definition used as molecular scalpels (scissors) to cut DNA in a precise & predictable manner. 2. Most restriction enzymes scan a DNA molecule looking for a specific sequence of 4 or 6 nucleotides (usually a palindrome site) ex: madam im adam, radar, hannah, GGCTCGG, ACTAGATCA, etc.
3. They are naturally occurring enzymes (proteins) found in bacteria and other organisms. Used by bacteria to slice & inactivate potentially dangerous DNA (virus). 4. Over 600 of these enzymes have been identified. 5. Native (self) DNA is protected from being cut.
6. Named after organisms they are extracted from. a. ECO RI Escherichia coli strain RY13 1 st one isolated. b. Bam HI Bacillus amyloliquifaciens strain H 1 st one isolated. c. Hind III Haemophilus influenzae strain Rd 3 rd one isolated.
Plasmids 1. Definition small rings of DNA. 2. Recombinant DNA (rdna): contains DNA from 2 different sources.
Gel Electrophoresis 1. Definition technique used to separate molecules based on charge, size & shape. (DNA, RNA, Proteins) 2. Medium used: agarose a polysaccharide derivative of agar. The gel is clear and resilient a thick jello but with pores to allow the molecules through.
3. Movement through gel: faster movement: smaller particles, greater charge, more compact shape. 4. Samples are placed in a well in the agarose slab. 5. The electrophoresis buffer (fluid) contains electrolytes that will allow electricity to conduct through the fluid. 6. Direct current voltage is supplied the higher the voltage, the quicker the sample moves.
DNA Fingerprinting Process 1. Tissue Used: blood, hair follicles, semen, skin, saliva 2. Amplify sample: use a process called PCR polymerase chain reaction 3. Add restriction enzymes 4. Gel electrophoresis 5. Compare banding patterns