Genetic Engineering

What is genetic engineering?

Definition: process of changing an organism’s genetic material to produce a new and useful result

This results in a transgenic organism (organism containing recombinant DNA)

Tobacco Plant that has had a firefly gene inserted into its cells, so it “glows”.

Why make transgenic plants and animals?

Food production Make plants that are resistant to pesticides and/or diseases

(Round-up® ready crops, crops resistant to certain viruses) Engineer food to stay fresh longer and ripen at the store Engineer some animals to grow larger without using

antibiotics or growth hormone. Protein production

Cows and goats could produce human proteins in milk Even plants can be used to produce human proteins Vitamin A in “golden rice”

Medical Research Use the “glow” gene to follow the expression of another

gene. Edible vaccines.

How does genetic engineering work? The desired (“donor”) gene is

isolated from the organism’s DNA using a restriction enzyme

Bacterial plasmid (“cloning vector”) is cut with same restriction enzyme Sticky ends of desired gene and plasmid

should be complementary Ligase (an enzyme) is added to help

seal sticky ends of plasmid and desired gene together

Last step: put the recombinant plasmid back into the bacteria

Example: Insulin Production

Protein that codes for insulin production is cut from human DNA using restriction enzyme (EcoRI)

Example: Insulin Production

Plasmid (from E.coli) is also cut with EcoRI Sticky ends are now

exposed on both human DNA and plasmid DNA

Example: Insulin Production

Ligase seals sticky ends of desired DNA and plasmid DNA

Recombinant DNA is inserted into a bacterium

Bacterium divides, producing 100’s of bacteria with the desired gene.

Why insert recombinant DNA into a bacterium?

Bacteria reproduce rapidly (some every 20 minutes) Inserted gene (e.g. insulin) is copied

(cloned) whenever bacteria make a copy of the plasmid

Results in a large amount of desired protein (insulin) in just a few days

How can you insert recombinant DNA into a host cell?

Transformation: use electricity, heat, or CaCl2 to “shock” cell into taking up plasmid

Microinjection: inject plasmid DNA directly into cell using microneedle

How can you insert recombinant DNA into a host cell?

Gene gun: coat tiny gold pellets with recombinant plasmid DNA and “shoot” into cell

How can you insert recombinant DNA into a host cell?

Viral vectors: Desired gene is placed into viral DNA and used to “infect” an organism’s cells without causing disease (virulence gene removed)