Transcript Why do these pigs glow in the dark? Genetic Engineering

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
X
Ligers are the
largest living
species of feline!
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:
–
–
–
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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.