Why do these pigs glow in the dark?

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

• Takes advantage of naturally occurring traits in a population

History of the English Bull Dog

• Bull dogs were bred in the 13th century.– The English wanted a dog they could use in bull-fighting

(a popular sport).

• 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 & eventually created 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.

Donkey + Horse = Mule Apple + Grape = Grapple

Male Lion + Female Tiger = Liger

Ligers are the largest living

species of feline!

X

Inbreeding

• Crossing 2 organisms that are very similar to 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.

Creating the Right Characteristics• If the desired characteristic is not present in an organism,

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).

Triploid bananas were created, because they are tastier & easy to eat.

HOWEVER, because the 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, without having to breed several generations of organisms.

Genetic Engineering

• If bacteria have a gene that would be beneficial for corn crops, we can cut the gene out & insert it into a corn plant’s DNA.

21st Century Genetic

Engineering

Genetically Engineered Organisms

• Genetically engineered organisms contain a gene(s) from another organism of the same or different species.– We eat genetically engineered vegetables for herbicide,

pesticide, & parasite resistance (GMOs).

• Transgenic Organisms: organisms that contain DNA from other species

Transgenic Bacteria

• Can produce substances from human genes– Human insulin for diabetes patients– Human growth hormone– Clotting factor for Hemophilia patients

Transgenic Plants

• Genetically modified foods– Seedless grapes & watermelon– Rice with vitamin enhancement– Pest-resistant crops (so chemical pesticides do not need to

be used)

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.

Why do these pigs glow in the dark?

Normal Pig Genes + GFP Jelly Fish Gene

GFP – Green Fluorescent Pigment

How do we make transgenic organisms?

First, we have to get the DNA we want 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.

EcoR1 cuts DNA only at the sequence –GAATC-

BamHI cuts only at –GGATCC-

• 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.

• 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.

1. Isolate the human gene & the bacterial plasmid.

2. Cut with the same restriction enzymes.

3. Once cut, the human gene can be inserted into the bacterial plasmid.

4. The bacteria takes up the plasmid & expresses the human gene.

Why use bacteria?

• Bacteria are used in genetic engineering for several reasons:– They reproduce quickly.– They’re simple.– They’re easily contained.– They take up genes from their surroundings.

Bacteria Cell Bacterial Plasmid

Transgenic bacteria that contain the GFP protein

from jellyfish – they glow under UV light.