Genetics and Biotechnology - Plant Root Genomics Consortium ...

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Genetics and Biotechnology

Biotechnology


A group of many technologies that
use living cells or their processes to
make products or solve problems




Used in basic and applied research



Used in developing products for the
marketplace

Fields Contributing to Biotechnology


Medicine


Plant Science


Food Science


Genetics


Biochemistry


Statistics


Mathematics


Engineering


Computer Science


Philosophy (Ethics)

Applications of Biotechnology


Cloning


Genes


Whole organisms


Drug production


Insulin


Disease prevention


HIV test


Blood
-
type test


Pregnancy test

Applications of Biotechnology


Genetic engineering


Gene therapy


Gene discovery


Human disease genes


Alzheimer’s


Breast cancer


Huntington’s Disease


Plant genes


Carotenoid synthesis


Oil production

Genetics Primer


Gene:

basic unit of heredity


Protein:

product of a gene


Genotype:

genetic makeup of an
individual (sum of all the genes)


Phenotype:

observed traits of an
individual, due to expression of its genes
and interaction with the environment

Genes are made of DNA

Cell

Nucleus

Sugar
-
phosphate backbone

Bases


DNA is a ladder
-
like double
helix.


Rungs of the ladder are
made of pairs of four bases:
A, C, G, T


Genes code for proteins


The sequence of bases in the DNA of a gene
contains information to make a protein


The DNA code is triplet


Each triplet codes for an amino acid


Example: the sequence TTG is the code for the amino acid
tryptophan


Proteins are built from amino acids


Transferring the information from DNA to protein
is called gene expression

protein

gene (DNA)

expression

Gene expression is regulated


The same set of genes is contained in (nearly)
every cell of an organism, but...


Not all genes are expressed in every cell


Genes for helping plants absorb minerals from the
soil are expressed in the root


Genes for plant oil production are expressed
primarily in the embryo


Genes for milk production in mammals are
expressed in the mammary glands

Proteins have many functions


Transport
:
hemoglobin carries oxygen in blood


Structural
:
collagen holds cells together


Receptor
:
receives signals sent to cell


Regulatory
:
control gene expression


Enzymes
:
catalyze chemical reactions in the cell

Proteins govern traits

An organism’s appearance and qualities are
the products of gene expression

Genes

Proteins

Traits

expression

=

Variation in traits is due to different alleles

Allele 1

Allele 2

Different forms of a gene (called alleles)

can lead to different phenotypes (expression of traits)

Gene A

Trait (Fruit Color)

Purple

White

Transmitting genes to offspring


Traditional mating or breeding


Female contributes half her genes through egg


Male contributes half his genes through sperm


Offspring have half their genes from mom and half
from dad


Genetic engineering


Donor contributes one or a few genes


Offspring have all their own genes plus one or a few
genes

“Breeding” vs. “Engineering”

TRADITIONAL BREEDING

GENETIC ENGINEERING

Desired gene

Donor

Commercial variety

New variety

Desired gene

Desired gene

(cross)

Desired gene

Commercial variety

New variety

(transfer)

=

=

(many genes transferred)

(one gene transferred)

Terms


Transgenic organism


One in which a gene has been introduced or
modified by genetic engineering


Genetically engineered organism (GEO)


Same as transgenic organism


Genetically modified organism (GMO)


Erroneously assumed to be same as transgenic
organism


Actually, organisms can be modified genetically by
“breeding” or by “engineering”

Applications of Biotechnology


Agricultural food production


Improved production


Disease resistance


Herbicide tolerance


Insect resistance




Improved food quality


Modified oils


Delayed fruit ripening


Nutritional enhancement

Insect resistance: Bt corn


Plants contain a gene from the soil bacterium,
Bacillus thuringensis



Bacillus thuringensis

strains contain genes for a
series of proteins called Bt toxins


Bt toxins:


are toxic to certain insects, including European corn
borer


break down rapidly in the soil


are not harmful to mammals or birds

Concerns


Environmental concerns


Effect of Bt corn on monarchs


Invasion of natural plant
populations by genetically
engineered crops



Food safety concerns


StarLink in taco shells



Farmer’s point of view

Impact of Bt corn on monarch butterflies


In 1999, an article* was published stating that
pollen from Bt corn plants could kill monarch
butterfly larvae


Assertion: planting of Bt corn poses a risk to
monarch butterflies


Concerns were raised and more research was
done

*
Losey et al., 1999. Transgenic pollen harms monarch
larvae. Nature 399:214.

Questions asked


Are the data
reproducible?


Does the lab represent
the field?


What controls should
be included?


What does monarch
reproductive behavior
say about the lab
experiment?


Is all Bt corn the same?


How does Bt corn
compare to impact of
current insect control
methods?


What is the greatest
documented threat to
monarch survival?


Is the monarch
endangered?

Findings


Some varieties of Bt corn produce pollen with
toxic levels of Bt; these are being phased out of
commercial production in favor of varieties do
not produce Bt in the pollen


In most parts of the country where corn is
grown, the time of monarch larvae feeding does
not coincide with the time that corn pollen is
shedding



More Findings


Pollen does not accumulate on the same leaves
as monarchs lay their eggs, even when
milkweed plants (preferred host) are found in
corn fields


The greatest threat to monarchs is predation.


Overall conclusion: Bt corn does not pose a
significant risk to monarch butterflies



Gatehouse et al., 2002. The case of the monarch
butterfly: a verdict is returned. Trends in Genetics
18:249
-
251.


The taco shell controversy


A variety of Bt corn called StarLink was detected
in taco shells and other foods


StarLink produces a variety of Bt toxin that had
not been tested for allergenicity in humans


Therefore, StarLink was approved by FDA only
for animal feed and not for human consumption

http://www.cbsnews.com/stories/2000/09/18/tech/main234240.shtml;
accessed 17 June 04

Risks to natural plant populations


Survival / reproduction of genetically engineered
crops outside cultivation


Pollen flow of genetically engineered crop to
wild relatives, hybrid formation, survival and
reproduction


Spread and persistence represent possible
economic or environmental harm

Wolfenberger and Phifer, 2000. The ecological risks and benefits of genetically
engineered plants. Science 290:2088.

Farmer’s view


45% of farmers had higher yields in fields of Bt
corn than conventional corn in 1998


Nearly 26% of farmers using Bt corn reported a
decrease in pesticide use


Even considering additional cost of planting Bt
corn (~$15/acre), Bt corn should pay off in 7 out
of 10 years


Bt corn can also reduce occurrence of
Fusarium

ear rot (spread by borers)

Applications of Biotechnology


Agricultural food production


Plants


Animals


Medical treatment


Biopharmaceuticals


Gene therapy


Environmental detoxification


Bioremediation


Phytoremediation

Animal production


Improving production through cloning


Strategy:

Good producer

Clones

(identical copies)

Interbreed

Cloned Animals


Dolly and Mom

Calf Clones

Medical treatments:

Biopharmaceuticals


Biological factors administered as drugs


Methods of production


purification from animals


purification from genetically



engineered organisms


Examples


insulin, for diabetes


human growth hormone, for genetic deficiencies


clotting factors for types of hemophilia

Using animals for pharmaceuticals:


Molecular “pharming”

Proteins from milk of transgenic animals

Lactoferrin




Clotting factor IX


Insulin
-
like growth factor

Iron supplement in

infant formula


Treatment of hemophilia


Treatment of diabetes

Medical treatments:

Gene therapy

David Vetter, the “Bubble Boy”

Severe Combined Immune Deficiency

Applications of Biotechnology


Agricultural food production


Plants


Animals


Medical treatment


Biopharmaceuticals


Gene therapy


Environmental detoxification


Bioremediation by bacteria


Phytoremediation by plants

Environmental detoxification:

Phytoremediation


Types of contaminants detoxified


heavy metals


radionuclides


organic compounds


petroleum products


explosives


Mechanisms plants use to detoxify


Accumulating heavy metals


Breaking down organic compounds


Volatilizing organic compounds

Phytodegradation


Enzymes in plant roots break down (degrade) organic
contaminants.


The fragments are incorporated into new plant materials.



contaminant

Phytoaccumulation


Nickel is removed from soil by moving into plant roots,
stems, and leaves.


Plant is then harvested and disposed of, and site is
replanted until nickel levels are acceptably low.

Genetics and Biotechnology