Genetic Engineering

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16 Δεκ 2012 (πριν από 4 χρόνια και 7 μέρες)

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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)