Genetic Engineering Part 3 - Bioenviroclasswiki

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14 Δεκ 2012 (πριν από 4 χρόνια και 8 μήνες)

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Genetic Engineering

Part 3


Genetically Modified
Organisms

4.4.9 State two examples of the current uses of
genetically modified crops or animals


A genetically modified organism (GMO) is one that has
had an artificial genetic change using the techniques of
genetic engineering such as gene transfer or
recombinant DNA. One of the main reasons for
producing a genetically modified organism is for it to
be more competitive in food production.

Transgenic plants


GM crops and GM animals are referred to as
genetically Manipulated organisms (GMO’s), also
known as transgenic organisms. Their genetic material
has been changed to include specific genes, usually
from another species.


Flavr

Savr


In 1994, the first genetically modified food sold commercially
was introduced. It was the “
Flavr

Savr
’ a tomato that was
genetically altered to stay fresh longer. This was achieved by
adding another gene that blocked the gene for the production
of an enzyme which caused rotting (
polygalcturonase
) due to
various commercial problems, the tomatoes are no longer
available.


Tomato salt tolerance


Another species of tomato was modified by a
bioengineering company to make it more tolerant to higher
level of salt in the soil. This makes it easier to grow in
regions of high salinity.
soil water results in desiccation,
wilting and death of the plant.



Tomato plants have now been genetically modified to carry
the gene for salt tolerance.


The origin of the gene was a weed called
Arabidopsis
thaliana
.


http://www.actahort.org/books/190/190_8.htm


THE DEVELOPMENT OF SALT
-
TOLERANT TOMATOES:
BREEDING
STRATEGIES





-


. One of the claims of the biotech industry is
that GM food could help solve the problem of
world hunger by allowing farmers to grow
food in various otherwise unsuitable
conditions. Critics point out that the problem
of world hunger in the world is one of food
distribution, not food production.


-


Majority of the American Soybean and cotton
crops are genetically modified.


Many of these GM plants have received
bacterial genes that make the plants resistant
to herbicides or pests. Farmers can more
easily grow these crops with far less tillage
and reduced use of chemical insecticides


Rice with Retinol


Retinol deficiency:


Retinol (Vitamin A1) is essential for the development of an effective
immune system, normal vision and growth. Where a child lacks Retinol
they have stunted growth and in extreme cases blindness. A serious
complication arises from the combined of malnutrition, disease and
retinol deficiency. The coincidence of these three conditions together is
seen in some third word nations. In Zambia more than 54% of the
population of children have retinol deficient diets. Even if children have
sufficient food (calories) the problem is that is not a balanced diet. These
children experience retarded growth for their age group and vision
problems are common. Vision problems usually begin with a loss of night
vision and then ultimately complete blindness. As might be expected
these communities find it very difficult to support children with these
multiple problems. To make matters worse diseases such as malaria and
measles (known killer diseases) disable or kill large numbers of children as
they have ineffective immune systems, another consequence of retinol
deficiency.

Rice with Retinol


Rice does not contain retinol or beta
-
carotene (used by the
body to make retinol).


Rice does contain a molecule that is normally used to make
beta
-
carotene.


The gene and enzymes to manufacture are missing from
rice.


Genetically modified rice contains the gene for the
manufacture of beta
-
carotene.


Source of the gene is either
Erwinia

bacterium or the
common daffodil.


The transgenic rice is usually yellow in
colour

because of
the accumulation of beta
-
carotene.


This transgenic rice is then crossed with local strains of rice.


Golden rice


Rice plants store vitamin A in their leaves but not in the rice
grains. Golden rice is genetically modified by adding genes
from daffodils and from a bacterium. This allows the rice to
store beta carotene, a precursor of vitamin A, in the grains,
which causes the yellow color. A new kind of Golden Rice
has now been produced, using one gene from maize and a
bacterium, which contains more than 20 times the amount
of beta carotene compared to the first kind of Golden rice.


This would provide a valuable source of vitamin A for many
people and could help prevent vitamin
-
A deficiency
-

and
resulting blindness
-

among half of the world’s people who
depend on rice as their staple food. but it has been met
with a lot of opposition from environmentalists and anti
-
globalisationists
.


Golden Rice


Herbicides: Round up


Weeds growing amongst a crop use up soil nutrients that would otherwise
be used by the crop plant.


This competition of resources reduces the productivity of the crop plant
and therefore the efficiency of farming.


Herbicides can be used prior to crop planting to kills weeds.


The herbicide cannot be used after crops have been sown as they will also
kill the crop.


The major herbicide in use is called '
Glyphosate
', anyone who has
gardened will know this as 'Roundup' which is the market name for the
product.


However, Cotton, Corn and Soybeans have been genetically modified to
contain an enzyme that breaks down
glyphosate
.


This makes these crops resistant to the herbicide.


Herbicide can then be used after the crop has grown to prevent the
reoccurrence of weed competition.



Factor IX : A human clotting factor is produces by genetically modified sheep.



The protein (factor IX) is expressed in milk from which it must be isolated before use by
haemophiliacs
.




A ewe is treated with fertility drugs to create super
-
ovulation.


Eggs are inseminated.



Each
fertilised

egg has the
transgene

injected.



must be isolated before use by
haemophiliacs
.





A surrogate ewe has the egg implanted for gestation.






Lambs are born which are transgenic, GMO for this factor IX gene.






Each Lamb when mature can produce milk.




The factor IX protein is in the milk and so must be isolated and purified before use in human.









must be isolated before use by haemophiliacs.




Genetically Modified Mice


Normally, mice do not contract polio because
they do not have the receptor in their cell
membranes that allows the polio virus to
infect their cells. Adding this receptor, means
that mice can be infected with polio and used
for experiments in order to study the disease
and its possible treatment and prevention.


GM mice infected with polio will develop
symptoms similar to humans with the disease

Transgenic animals


One way of genetically engineering an animal is to get
it to produce a substance which can be used in medical
treatment. Consider the problem faced by some
people with a blood condition in which their blood
does not clot because they lack a protein called factor
IX. If such people can be supplied with factor IX, their
problem will be solved. The least expensive way of
producing large amounts of factor IX is to use
transgenic sheep. If a gene which codes for the
production of factor IX is associated with the genetic
information for milk production in a female sheep, she
will produce that protein in her milk.


Future ?


In the future a wide variety of genetic
modifications may be possible. Perhaps
inserting genes to make animals more
resistant to parasites, to make sheep produce
pre
-
dyed wool of any chosen color, to produce
prize
-
winning show dogs, faster race horses…






Bt corn is genetically modified maize. A gene from
Bacillus
thuringiensis

(Bt) has been incorporated into the maize
DNA. As a result, the plants produce a toxin that makes
them resistant to insects. Bt crops are grown in the
US


Bt corn contains a gene from the
Bacillus
thuringiensis

which produces a protein that is toxic to specific insects, in
particular the European corn borer (ECB) which is also
found in the US.


The ECB through stems and leaves of the corn plant and will
damage vascular bundles and disrupt the transport of
water and nutrients through the plant. It can also weaken
the stems and leaves so that the plant or leaves may break.
Only a small part of the damage is caused by the ECB eating
the corn directly.


4.4.10 Discuss the potential benefits and Possible harmful
effects of one example of genetic modification


The damage caused by the ECB is much reduced.


Bt corn is slightly more expensive, but the difference is less than one extra
application of insecticide.


Non
-
Bt corn needs to be checked often for signs of ECB
-

less checking
needed for Bt corn.


Less insecticide needed means less impact on the environment and lower
health risks for the workers.


Seems to reduce the infection with fungus so
myotoxins

levels are
lowered.
Myotoxins

are difficult to remove by cooking/freezing and may
go into the food chain and may be found in meat of animals which ate the
infected corn.
Myoptoxins

can be a hazard to human and animal health.


Less pest damage and therefore higher crop yields to help to reduce food
shortages.


Less land needed for crop production, so some could become areas for
wildlife conservation.


Harmful effects of Bt corn



Insects may develop resistance to Bt toxins because they are
exposed to it all the time.


Resistant insects also make Bt spray useless as insecticide (Bt spray
is considered to be relatively safe for humans and environment)


It is difficult to prevent pollen (with the Bt gene) from travelling
outside the field where the Bt corn is grown.


It may fertilize non
-
Bt corn e.g. organically grown corn which can
then no longer be sold as organic corn.


It may fertilize wild relatives and make them more resistant to
insects and have them dominate the niche they live in. Populations
of wild plants might be changed. Cross
-
pollination will spread the Bt
gene into some wild plants but not others. These plants would then
produce the Bt toxin and have an advantage over other wild plants
in the struggle for survival. This would result in loss of biodiversity


Click 4


The benefits of GMO include:


Increased yields particularly in regions of food shortage.


Yields of crops with specific dietary requirement such as vitamins
and minerals.


Crops that do not spoil so easily during storage.


GM animals produce similar effect including higher meat yields.


The disadvantages or concerns about GMO usually can be found:


The foods (animal and plant) are considered un
-
natural and unsafe
for human consumption.


There is a risk of the escape of 'genes' into the environment where
they may be passed to other organisms with unknown effects.



Humans or farm animals that eat the genetically
modified maize might be harmed by the bacterial
DNA in it, or by the Bt toxin.


Insects that are not pests could be killed. Maize
pollen containing the toxin is blown onto wild
plants growing near the maize. Insects feeding on
the wild plants including monarch butterfly
caterpillars, are therefore affected even if they do
not feed on the maize.






Is genetic engineering a good or bad thing?


Benefits, promises, and hopes for the future




GM crops will help farmers by improving food production.


GM crops which produce their own pest
-
control will be beneficial to
the environment because fewer chemical pesticides will be needed.


Using GMO’s to produce rare proteins for medications or vaccines
could be, in the long run, less costly and produce less pollution than
synthesizing such proteins in laboratories.


Farmers can be more in control of what crop or livestock they
produce. There is always some randomness in breeding; genetic
modification makes the process less of a gamble. It is also much
quicker than selective breeding.


The multinational companies who make GM plants claim that they
will enable farmers in developing nations to help reduce hunger by
using pest
-
resistant crops or GM plants which need less water.


Harmful effects, dangers and fears.



No one knows the long term effects of the GMO’s in the wild.
Efforts to keep the GM plants under control in well
-
defined areas
have failed and pollen from crop has escaped to neighboring fields.
Genes from GM plants could be integrated into wild species giving
them an unnatural advantage over other species and an ability to
take over the habitat.


Bt crops which produce toxins to kill insects could be harmful to
humans because, unlike chemical pesticides which are only applied
to the outer surface the toxins are found throughout the plant.


There are risks for allergies; if someone is not allergic to natural
tomatoes but is allergic to GM tomatoes, they will need to know
which one they are eating. But there is no difference in the outward
appearance of the fruit and food labeling is not always clear.

Issues raised by Genetic Engineering


Will a gene, added to a genome, function in an
unforeseen manner
-
perhaps, for example, triggering
some disease in the recipient?


Might an introduced gene for resistance to adverse
conditions get transferred from a crop plant or farm
animal into a weed species or to some predator?


Is it possible that a harmless organism such as the
human gut bacterium
E.coli

might with recombinant
DNA technology, be transformed into a harmful
pathogen that escapes the laboratory and infects the
population?



Is there an important overriding principle that
humans should not ‘change nature’ in a
deliberate way?


Genetic engineering is a costly technology, mostly
beneficial to the health and life expectancy of
people of developed nations. If the funds were
made available for more basic problems of
housing, health and nutrition in less developed
countries instead, vastly more humans would
benefit immediately.


Bt Corn


TOK are GM crops safe?


Genetic modification is illegal in some countries but widely
encouraged in others. There are risks that must be carefully
considered and weighed against the potential benefits.


Would the more than 250,000 people who go blind each
year from Vitamin A deficiency welcome genetically
modified ‘golden rice, in which each grain contains Vitamin
A, or protest against its development?


How seriously are the concerns of those opposed to genetic
modification taken?


Does protesting make the world a better place to live in?


How should we decide how we use knowledge?

4.4.6 Outline three outcomes of the sequencing
of the complete human genome


Dr Francis Collins and Dr Craig Venter, the leaders of the Human Genome
Project.


The human genome project is an effort to map the human genome in
total detail by determining the entire nucleotide sequence of human
DNA. Because the genome of an organism is a catalogue of all the bases
it possesses, the Human Genome Project helped to determine the order
of all the bases A, T, C and G in human DNA.


The human genome can be thought as a map which can be used to show
the locus of any gene on any one of the 23 pairs of chromosomes.


In sex linked diseases, it is relatively easy to determine which
chromosome the gene responsible for the disease is found on; often the
locus is on the X chromosome
.


The ultimate objectives of HGP were to discover the location of each
human gene and the base sequence within its DNA structure.


-


Another advantageous use of the human
genome is the production of new medications.
This idea involves several steps.


Find beneficial molecules which are produced
naturally in healthy people;


Find out which gene controls the synthesis of a
desirable molecule.


Copy that gene and use it as instructions to
synthesize the molecule in a laboratory;


Distribute the beneficial molecule as a new
medical treatment.


-


By comparing the genetic makeup of
populations around the world, countless
details could be revealed about ancestries
and how humans have migrated and mixed
their genes with other populations over time


Benefits of human genome



Provides
insight into fundamental mysteries as embryonic
development and evolution.



For human health, the identification of genes will aid in the
diagnosis, treatment, and possibly prevention of many of our
more common ailments, including heart diseases, allergies,
diabetes, schizophrenia, alcoholism, Alzheimer’s disease and
cancer. Hundreds of disease
-
associated genes have already been
identified as a result of the project.


The production of medicines (based on DNA sequences) to cure
diseases and/or genetic engineering to remove the genes which
cause the disease.


To determine fully which genetic disease any individual is prone to
(genetic screening leading to preventive
medicine);

-


The DNA sequences from the HGP are deposited
in a database available to researchers all over
the world via the Internet. Scientists use
software to analyze the sequences. The most
exciting challenge is figuring out the functions of
the genes and how they work together to direct
the structure and function of a living organism.


Make use of the handout on HGP given to you
from IB Biology Text book by
C.J.Clegg

(Page
numbers 131
-
133)

Outcome of the HGP

Click
4 Biology


identify all the approximate 30,000 genes in human DNA.


determine the sequences of the 3 billion chemical base
pairs that make up human DNA.


store this information in database.


improve tools for data analysis.


transfer related technologies to the private sector.


address the ethical, legal, and social issues (ELSI) that may
arise from the project.


To help achieve these goals, researchers also are studying
the genetic makeup of several nonhuman organisms. These
include the common human gut bacterium Escherichia coli,
the fruit fly, and the laboratory mouse.