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Selective Breeding (Ch. 13.1)
Remember… Selective
breeding is used to produce plants and animals with desired traits.
Genetic Engineering (Ch. 13.2)
Genes are isolated, modified, and inserted into an organism
Made possible by recombinant technology
Cut DNA up and recombine pieces
Amplify modified pieces
Genetically modified organisms are called transgenic organisms.
TRANSGENIC ANIMALS
1. Mice – used to study human immune system
2. Chickens – more resistant to infections
3. Cows – increase milk supply and leaner meat
4. Goats, sheep and pigs – produce human
proteins in their milk
Transgenic Goat
Human DNA in a goat cell
This goat contains a human gene that codes for a blood clotting agent. The blood clotting agent can be harvested in the goat’s milk.
Restriction Enzymes
Molecular scissors that cut DNA at a specific nucleotide sequence
Over 200 different restriction enzymes are known, each isolated from bacteria and able to cut DNA in a unique manner
Scientists use restriction enzymes in the process of genetic engineering.
Recombinant DNA Technology
“Cutting and Pasting”
Enzymes: Restriction
enzymes = “cut”
Ligase = “paste”
DNA (Gene) cloning
Want to study or isolate a particular gene Need to get many copies (amplification) of the
gene so it can be studied adequately Most organisms only have one or two copies of
any gene per cell, so we need a way to amplify copies of that gene
Do that via cloning into a vector This allows scientists to make additional copies
of the gene using bacteria
Using Plasmids
Plasmid is small circle of bacterial DNA
Foreign DNA can be inserted into
plasmid
Forms recombinant plasmids
Plasmid is a cloning vector
Can deliver DNA into another cell
Polymerase Chain Reaction (PCR)
PCR allows scientists to make many copies of a piece of DNA.
1. Heat the DNA so it “unzips”.
2. Add the complementary nitrogenous bases.
3. Allow DNA to cool so the complementary strands can “zip” together.
Polymerase Chain Reaction
Double-stranded DNA to copy
DNA heated to 90°– 94°C
Primers added to base-pair with ends
Mixture cooled; base-pairing of primers and ends of DNA strands
DNA polymerasesassemble new DNA strands
Figure 16.6Page 256
Stepped Art
Polymerase Chain Reaction
Figure 16.6Page 256
Stepped Art
Mixture heated again; makes all DNA fragments unwind
Mixture cooled; base-pairing between primers and ends of single DNA strands
DNA polymerase action again doubles number of identical DNA fragments
Gel Electrophoresis
DNA is placed at one end of a gel A current is applied to the gel DNA molecules are negatively charged
and move toward positive end of gel Smaller molecules move faster than larger
ones Function- to separate DNA fragments
What are these techniques used for? Forensic: identifying criminals & victims Identifying disease genes in animals &
humans Gene Therapy: inserting of new working
copies of genes into humans Animal knockouts: turning off of a specific
gene in order to discover its function
Engineered Proteins
Bacteria can be used to grow medically
valuable proteins
Insulin, interferon, blood-clotting factors
Vaccines
Engineered Plants
Cotton plants that display resistance to herbicide
Aspen plants that produce less lignin and more cellulose
Tobacco plants that produce human proteins Mustard plant cells that produce
biodegradable plastic
Cloning Dolly
1997 - A sheep cloned from an adult cell
Nucleus from mammary gland cell was
inserted into enucleated egg
Embryo implanted into surrogate mother
Sheep is genetic replica of animal from
which mammary cell was taken
The Human Genome Initiative
Goal – Sequence all human DNA Initially thought by many to be a waste of
resources Sequencing was mostly completed ahead
of schedule in early 2001