chapter 13 genetic engineering. genetic variation how are a great dane and a chihuahua similar? how...
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Genetic variation
• How are a great dane and a chihuahua similar?• All dogs are the same species• LOTS of genetic variation!
• How did this happen?• We did it!
Selective breeding
• Selective breeding: a method of breeding organisms with desired characteristics to provide the next generation with that trait
• Takes advantage of natural genetic variation
• Luther Burbank- selectively bred disease-resistant potatoes
hybridization
• Hybridization: breeding technique that crosses dissimilar individuals to bring together the best traits of each
• Hybrid: offspring of hybridization
• Ex: crossing a large sized potato with a potato that is disease-resistant
Or a hybrid car…
…or a mule!
inbreeding
• Inbreeding: continued breeding of individuals with similar (desired) characteristics
• You get the desired traits but…• Increased chance of other defects (ex:
2 recessive alleles)
Genetic variation
• Increased genetic variation = possibility of breeding mutants (but this is a good thing)• Remember the 4 criteria for a gene?
• Mutations are the BIGGEST source of genetic variation
• Whether good or bad, mutations are new to a population and increase diversity
Producing new kinds of organisms
• Treat with radiation or chemicals to mutate
• Bacteria• small and multiply quick/easy to
pass along mutation• Ex: bacteria that digest oil (used in
oil spills)
• Plants• Chemicals prevent chromosome
separation in meiosis• End up with extra sets of
chromosomes (polyploids)
13-2 Manipulating DNA
• What does it mean to “manipulate” DNA?• To change it!
• Selective breeding and inbreeding use natural genetic variation…but its unpredictable!
• Now, we can “rewrite” the code
How do we change dna?
• Must have knowledge of structure and chemical properties
• New technology:• 1. extraction techniques• 2. cut into smaller pieces• 3. identify base sequences• 4. make unlimited copies
1. Dna extraction
• Like in our strawberry lab!
• Open up the cell and nucleus
• Separate DNA from everything else
2. Cutting dna…
• Restriction enzymes: enzyme that cuts DNA at a specific sequence of nucleotides• Very specific
• Recombinant DNA: DNA produced by combining DNA from different sources• Ex: human insulin gene and pig DNA- have
pigs produce insulin
…and separating DNA
• Gel electrophoresis: procedure used to separate + analyze DNA fragments• Place DNA (- charge) at one end of a
gel and apply + charge to the other• Fragments move across gel- smaller
move faster/further• Used to compare/contrast/identify
particular genes
3. Identifying base sequences
• Used to study specific genes, compare, discover functions, etc.
• To “read” the sequence = determine the order of bases
• Sequencing:• Start with unknown strand + DNA
polymerase +nucleotide bases = complimentary strand is made
• Bases are dyed to identify them
• Now, everything is automated
4. Making copies
• Polymerase chain reaction (PCR): technology that allows scientists to make many copies of a gene
• How it works:• Heat DNA- strands separate• Cool and add primers- short pieces of DNA that
tell DNA polymerase to start working• Add free nucleotide bases + DNA polymerase• Makes a new stand- like artificial DNA
replication!
13-3 cell transformation
• What is transformation?
• Taking in DNA from outside the cell- this “external” DNA then becomes part of the new cell’s DNA• DNA MUST be integrated into
a chromosome!
• Recombinant DNA!
Transforming bacteria
• Plasmid: small circular DNA molecule
• Why plasmids?• Replicate easily so foreign
DNA will then be replicated• Genetic marker: a gene that
distinguishes bacteria with foreign DNA plasmid from ”regular” bacteria• Antibiotics resistant genes
used alot
Transforming plant cells
• Use bacterium that inserts a plasmid with manipulated foreign DNA into plant cells
• Can also:• Take up DNA when cell wall is removed• Inject DNA directly into plant cells
• Either way, DNA MUST be integrated into the chromosome
Transforming animal cells
• Cells are large enough for direct injection of DNA
• Enzymes used to cut and insert DNA into chromosome
• May also use genetic markers
• Gene replacement- replace one gene with another
13-4 Applications of ge
• GE = biotechnology
• Can we combine plant and animal genes?• YES!
• Luciferase enzyme (firefly glow) + tobacco plant = a glowing plant
Transgenic organisms
• Transgenic organism: an organism that contains genes from a different organism
• Gene from one inserted into the cell of another
• These transformed cells = a new organism!
Transgenic microorganisms
• Insert human gene for proteins into bacteria
• Bacteria used to “harvest” human proteins• Ex: insulin, growth factors, clotting
factors
Transgenic plants
• Examples:• Plants with natural insecticides• Plants that will resist weed-killing
chemicals• Rice with added vitamin A
Transgenic animals
• For research:• mice with human immune systems
• For food:• Livestock with added growth hormone-
grow faster/leaner• Chicken that is resistant to food
poisoning bacteria• Milk that produces human proteins in
it
cloning
• Clone: a member of a population of genetically identical cells produced from a single cell
• Single-celled bacteria= easy to clone
• Multicellular organism= more difficult
• “Dolly” the sheep- cloned by Ian Wilmut in 1997
How did he do it?
• De-nucleate an egg cell
• Donor nucleus fuses to the de-nucleated cell• Fused using an electric shock
• Cell will begin to divide- form an embryo
• Embryo is placed in foster mom’s uterus
• Development and birth happen as normally does
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