Bt

roachavocadoBiotechnology

Dec 14, 2012 (4 years and 6 months ago)

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Biotechnology

Biotechnology


Techniques used to manipulate DNA


Many applications:


Medical


Animal science

»
Bacterial production of BST to increase milk production


Horticultural

»
Bacterial production of human insulin

»
Transgenic crops with herbicide resistance or nutrient
enhancement


Stages of genetic engineering

Biotechnology


DNA cleavage


Source DNA (with gene of interest) broken into fragments
by enzymes


DNA fragments visualized by electrophoresis


Bigger
fragments
move through
gel more
slowly when
electric current
applied


Stages of genetic engineering

Biotechnology


Production of recombinant DNA


DNA fragments inserted into viral or bacterial DNA
(=recombinant DNA)


e.g. DNA
from source
inserted into
circular
chromosome
of bacteria
called
plasmid


Stages of genetic engineering

Biotechnology


Cloning


Bacteria or virus with source DNA introduced into cells of
interest (often bacteria)


Cells reproduce asexually to produce clones


Cells with
different
fragments
maintained
separately
(produce
clone
library)


Stages of genetic engineering

Biotechnology


Screening


Clones with DNA fragment of interest (fragment with
desired gene) identified


Bacterial
plasmid contains
gene for
antibiotic
resistance


Cells without
plasmid
fragments
susceptible to
antibiotic

STEP 1: remove
cells without
plasmid


Stages of genetic engineering

Biotechnology


Screening


Clones with DNA fragment of interest (fragment with
desired gene) identified


Bacterial
plasmid contains
gene for enzyme
that metabolizes
sugar (X
-
gal)


If source DNA
inserted in this
gene, no sugar
metabolism
occurs

STEP 2:
eliminate cells
without
source DNA


Stages of genetic engineering

Biotechnology


Screening


Clones with
DNA
fragment of
interest
identified


Hybridization
used to locate
gene of
interest

Step 3: locate gene of interest


Horticultural applications of genetic engineering

Biotechnology


Produce transgenic plants


Horticultural applications of genetic engineering

Biotechnology


Ethylene inhibition


Carnations insensitive to ethylene last longer when cut


‘Flavr savr’ tomatoes in which ripening is delayed (resist
over ripening in transport)


Horticultural applications of genetic engineering

Biotechnology


Herbicide resistance


Transgenic soybeans tolerant to active ingredient in
Roundup, a commonly used herbicide


In 1999, 50% of soybeans in US transgenic strains


Used in many
other plants
(e.g. petunia)


Horticultural applications of genetic engineering

Biotechnology


Nitrogen fixation


Incorporate genes of nitrogen
-
fixing bacteria into crops
to reduce the use of fertilizers

Root nodule
containing
nitrogen
-
fixing
bacteria


Horticultural applications of genetic engineering

Biotechnology


Insect resistance


Incorporate
Bt

gene into crops


Bt

gene produces protein that is toxic when ingested by
insect larvae


Approved by EPA for potato, cotton, tobacco, corn,
tomato and other crops


Possible detrimental effects on harmless insects such as monarch
butterflies


Horticultural applications of genetic engineering

Biotechnology


Added
nutrients