Recombinant DNA and Genetic Engineering Chapter 13

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

What do you think about eating genetically modified foods?

Genetically modified organisms are called transgenic organisms. TRANSGENIC ANIMALS Mice – used to study human immune system Chickens – more resistant to infections Cows – increase milk supply and leaner meat 4. Goats, sheep and pigs – produce human proteins in their milk

Transgenic Goat 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. Human DNA in a goat cell

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.

Restriction enzymes

Recombinant DNA The ability to combine the DNA of one organism with the DNA of another organism.

Recombinant DNA Technology “Cutting and Pasting” Enzymes: Restriction enzymes = “cut” Ligase = “paste”

Therefore, a recombinant DNA molecule contains different regions from different sources

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

Using Plasmids

Polymerase Chain Reaction (PCR) PCR allows scientists to make many copies of a piece of DNA. 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 Polymerase Chain Reaction 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 polymerases assemble new DNA strands Stepped Art Figure 16.6 Page 256

Polymerase Chain Reaction 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 Stepped Art Figure 16.6 Page 256

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

Gel Electrophoresis

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

DNA Fingerprinting

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

Ethical Issues Who decides what should be “corrected” through genetic engineering? Should animals be modified to provide organs for human transplants? Should humans be cloned?