Normal Pig Genes + GFP Jelly Fish Gene GFP – Green Fluorescent Pigment
Genetic Engineering What are some ways that we use genetics to our advantage?
Selective Breeding • Process in which 2 individual organisms with desired characteristics are chosen to produce the next generation of offspring • This process has been occurring for thousands of years! • Dog Breeds, Agriculture Can you think of any examples? • Takes advantage of naturally occurring traits in a population
History of the English Bull Dog • Bull dogs were bred in the 13th century for a purpose! • The English wanted a dog they could use in bull-fighting (a popular sport back then). • The bull dogs would bite the bull’s neck & lock it’s jaws so that the bull couldn’t escape or fight back. • For this reason, they bred dogs with strong jaws & flat faces to create the bull dog! The bull dog was bred from the mastiff.
Hybridization • The crossing of 2 dissimilar organisms to get the best of both organisms • Hybrids are often hardier & stronger than either parent! Lion + Tiger = Liger Donkey + Horse = Mule
Inbreeding • Crossing 2 organisms that are very similar to retain (keep) desirable characteristics • Recessive genetic disorders can appear more frequently. WHY? Maintaining purebred dog breeds often requires inbreeding. Dog breeders have to be very careful about genetic disorders!
Increasing Variation • If the desired characteristic is not present, scientists can induce mutations in hopes of it causing the right effect! • Success stories: • Oil-eating bacteria: used to clean up oil spills • Creating polyploidy (3+ chromosomes) plants – usually larger & stronger
The bananas you buy at the grocery store are triploid (3 sets of chromosomes)! Because the hybrid bananas are triploid, they’re sterile! The black spots in the hybrid bananas are aborted ovules, which would have become seeds.
Genetic Engineering • That was the “old” way of manipulating genetics! • Now, we can isolate specific DNA sequences & modify the genetic code directly!
Genetic Engineering • For example, if bacteria have a gene that would be beneficial for corn crops, we can cut the gene out & insert it into a corn plant!
Genetic Engineering • Genetically engineered organisms contain a gene(s) from another organism of the same or different species. • We eat genetically engineered vegetables for parasite resistance!
Applications of Genetic Engineering • Transgenic Organisms: organisms that contain DNA from other species • Transgenic Bacteria: • Produce human insulin for diabetes patients • Human Growth Hormone • Clotting Factor (Hemophilia)
Transgenic Organisms • Transgenic Animals: • Allow us to study human genes in animals • Produce organisms that can make human proteins Cows with multiple copies of a growth hormone grow faster & bigger!
Transgenic Organisms • Transgenic Plants: genetically modified foods • Seedless grapes & watermelon • Rice with vitamin enhancement • Pest-resistant crops (so chemical pesticides do not need to be used)
First, we have to get the DNA out of the cell. • DNA Extraction: lysing (bursting) cells & separating the excess cell parts from the DNA by using a centrifuge Dissolved DNA Cell Junk
Next, use restriction enzymes. • The gene that we wish to insert into another genome must 1st be cut out of the original genome using a restriction enzyme. • Restriction Enzymes: proteins found in bacteria that cut both strands of DNA only at specific sequences
Restriction Enzymes There are hundreds of restriction enzymes, each cuts DNA at a specific sequence!
Many REs leave DNA pieces with staggered ends called “sticky” ends. • This is because they have nucleotides that are exposed & can easily join back together with a complementary DNA strand.
Recombinant DNA • Manipulating the presence or absence of a gene by adding or cutting out gene sequences • Combining DNA from 2 different sources by cutting with the same enzymes creates DNA that has been modified.
A gene that you wish to recombine in another organism’s genome must 1st be put into a vector. • Vector: used to carry the piece of DNA that was cut; this is usually a virus or plasmid found in bacteria. • Plasmid: a small circular DNA molecule found in bacteria
Lastly, use the vector to insert the gene into the host cells. • Once the gene has been inserted into the host cell, each time the host cell divides the daughter cells will carry the gene. Viruses work well as vectors, because they target specific cells. Once attached to the host cell, they insert the gene into the cell.
Transformation • A cell takes in DNA from outside the cell & incorporates it into its own DNA • Bacterial plasmids, chromosomes in plants & animals
Why do we do this again? • Produce protein products for use • Prepare many copies of the gene itself • Enables scientists to determine the gene’s nucleotide sequence • Provide an organism with a new metabolic capability by transferring a gene from another organism Some diabetes patients have to inject themselves with human insulin. This human insulin is mass produced by bacteria!
Bacteria are most commonly used as host cells. Why?! • DNA can be easily isolated & reintroduced into bacterial cells. • Bacteria cultures also grow quickly, rapidly replicating the foreign genes. • Bacteria will also produce large amounts of the protein of interest.