Genetic Engineering

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 CaCl
2

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)