Transcript Biology: 11.2 Human Applications Genetic Engineering

Biology: 11.2 Human Applications Genetic Engineering
Human
Applications
Genetic
Engineering
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
The Human Genome Project:
 The Human Genome Project is a
research project linking 20 labs
in six countries.
 Teams of scientists in the
project worked to identify and
map all 3.2 billion base pairs of
all the DNA that makes up the
human genome.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
The Human Genome Project:
 One of the most surprising
things about the human genome
is the large amount of DNA
that does NOT encode proteins.
 In fact, only about 1 to 1.5% of
the human genome is DNA that
codes for proteins. Each human
cell contains about 6 feet of
DNA but less than 1 inch is
devoted to exons.
 (recall that exons are
sequences of nucleotides that
are transcribed and translated)
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
The Human Genome Project:
 Exons are scattered about the
human genome in clumps that
are not spread out evenly among
the chromosomes.
 On most human chromosomes,
great stretches of
untranscribed DNA fill the
chromosomes between the
scattered clusters of
transcribed genes.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
The Number of Human Genes:
 When they examined the complete
sequence of the human genome,
scientists were surprised at how
few genes their actually are .
 Human cells contain about 30,000
to 40,000 genes. This is only
about double the number of genes
in a fruit fly.
 It is only about one quarter of the
120,000 genes scientists had
expected to find.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
The Number of Human Genes:
 How did scientists make such a
large mistake estimating the
number of genes?
 When scientists had counted
messenger RNA (mRNA) they
had found over 120,000. Each
of these can in turn be
translated into a unique
protein.
 Scientists had “expected” to
find as many types of genes as
their were different types of
mRNA molecules.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
 Drugs: Many genetic disorders and human
illnesses occur when the body fails to make
critical proteins.
Juvenile diabetes is such an illness.
 The body is unable to control levels of
sugar within the blood because a critical
protein, insulin, cannot be made.
 These failures can be overcome if the
body can be supplied with more of the
protein it lacks.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
 Today, pharmaceutical companies
worldwide produce these medically
important proteins using bacteria and
genetic engineering in combination.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
 Today many genetically engineered
medicines are used to treat everything
from burns to diabetes.
 Examples include:
 Erythropoetin for anemia
 Growth factors for treating burns,
ulcers
 Human Growth Hormone for growth
defects
 Insulin for diabetes
 Interferons for viral infections and
cancer
 Taxol for ovarian cancer
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
Vaccines:
 Many viral diseases, such as smallpox and
polio, cannot be treated by existing drugs.
Instead, they are combated by prevention
through use of vaccines.
 A vaccine is a solution containing all or part
of a harmless version of a pathogen
(disease-causing microorganism).
 It is a weakened version of the disease;
incapable of causing serious harm”
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
Vaccines:
 When a vaccine is injected, the immune
system reads the pathogen’s surface
proteins and responds by making defensive
proteins called antibodies. The immune
system creates a defense system against
this form of the disease.
 In the future, if the same pathogen enters
the body, the antibodies are now there to
combat the pathogen and stop it’s growth
before it can cause a disease. The immune
system stays in place so when the flu or
cold strikes in full force, the antibodies
are already there to fight it before it can
11/1/2009
grow.
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
Vaccines:
 Traditionally, vaccines have been prepared
by either killing a pathogenic microbe or by
making the microbe unable to grow.
 The disease causing microbe is rendered
into a “weakened form” ; strong enough to
cause a reaction in the immune system but
not strong enough to make the taker ill.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
Vaccines:
 This ensures that the vaccine itself will not
cause the disease but only activate the
antibodies to form.
 With these types of vaccines there is
always some small danger for getting sick
as some people are more sensitive to the
vaccine. Their threshold is lower.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Genetically Engineered Drugs and Vaccines:
Vaccines:
 Vaccines made by genetic engineering avoid
this danger and are less likely to risk
infection to those who are extra-sensitive
to the microbes.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Dna Fingerprinting:
 Other than identical twins, no two
individuals have the same genetic material.
 Scientists use DNA sequencing technology
to determine a DNA fragment’s nucleotide
sequence.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Dna Fingerprinting:
 Because the places a restrictive enzyme
can cut depend on the DNA sequence, the
lengths of the DNA fragments will vary
between any two individuals.
 A DNA fingerprint is a pattern of dark
bands on photographic film that is made
when an individuals DNA restriction
fragments are exposed to an X-ray film.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Dna Fingerprinting:
 Because these bandings are unique to every
individual, they are like fingerprints.
 The banding patterns from any two
individuals can be compared to determine if
they are related.
 Because fingerprinting can be performed
on a sample of DNA from blood, bone, or
hair; DNA fingerprinting is used in
forensics as a tool.
11/1/2009
Biology: 11.2 Human Applications Genetic Engineering
Dna Fingerprinting:
 DNA fingerprinting can also be used to
identify the genes that cause genetic
disorders, such as Huntington’s Disease and
Sickle cell Anemia.
11/1/2009
Computer Lab:
 Use the internet to go online and write a one
paragraph mini-report on the following topic: DO NOT
COPY CUT OR PASTE:
 How is DNA fingerprinting used in the science of
modern forensics to solve crimes?
11/1/2009
Biology 11.3 Genetic Engineering in Agriculture
Genetic
Engineering in
Agriculture
11/7/2009
Improving Crops
 Farmers began primitive genetic
breeding years ago by selecting
seeds from their best plants,
replanting them, and gradually
improving the quality of their crops
over time.
 Today, we use genetic engineering
to select and add characteristics
and modify plants by manipulating a
plant’s genes.
11/7/2009
Improving Crops
 Genetic engineering can change
plants in many ways; from making
plants drought resistant to making
plants that can thrive in different
soils, climates or environmental
conditions.
11/7/2009
Improving Crops
 Genetic engineers have developed
crop plants that are resistant to a
biodegradable weedkiller called
glyphosate. This enables farmers to
spray their fields with glyphosate,
kill all the weeds off, and leaves the
crops unharmed.
 Half of the 72 million acres of
soybeans planted in the U.S. in 2000
were genetically modified to resist
glyphosate.
11/7/2009
Improving Crops
 Scientists have also developed crops
that are resistant to certain insects
by inserting specific genes into
plants.
 This added gene makes the plants
produce proteins that make the
plant unacceptable to the insects
for a food source.
11/7/2009
More Nutritious Crops
 Genetic engineering has been able,
in many instances, to improve the
nutritional value of many crops.
 For example, in Asia , rice is a major
food crop. Rice however is low in
iron and beta-carotene.
 Genetic engineers have modified
rice in these countries by adding
genes which boost the levels of iron
and beta-carotene to the rice
plants.
11/7/2009
Risks of Modified Crops
 Risks: Many people, including many
scientists, have expressed concern
that genetically modified crops (GM
crops) might turn out to be
dangerous.
 What kind of unforeseen negative
affects might we experience from the
new engineered crops?
 Potential problems:
We have already noted that crops
such as soybeans have been
genetically altered to make them
resistant to the weedkiller
glyphosate.
 Scientists are concerned that the
use of glyphosate will lead to weeds
that are immune to this weedkiller.
Than we will need to search for a
new weedkiller and alter more crops
11/7/2009
to
be resistant to it.
Risks of Modified Crops
Are GM crops harmful to the
environment?
 Will genes introduced into crops by
genetic engineering pass on to wild
varieties of plants?
 This type of gene flow happens all the
time between related plants.
 In most crops however, no closely related
wild version of the plant is nearby to
take up the gene changes.
 Some scientists fear that insect
pests may become immune (by
adapting) to the toxins that are
genetically engineered in some
plants.
 This would lead to insect strains that are
harder to kill as they would be immune to
the genetically produced changes that
were supposed to repel them.
11/7/2009
Gene technology in Farm Animals
 Farmers have, for generations,
improved their stock of animals
through selection of the best and
cross breeding.
 Now, many farmers use geneticallyengineered techniques to improve
their stock or their production.
 Many farmers add growth hormone to
the diet of their cows to increase the
amount of milk their cows produce.
The cow growth hormone gene is
introduced into bacteria which is than
added to the cow’s food supply.
 This increases the amount of milk the
cow produces.
 Scientists have also boosted growth in
pigs by adding growth hormone genes
to the food that pigs eat. These
procedures lead to faster growth and
higher profits for farmers.
11/7/2009
Making Medically Useful Proteins
 Another way in which gene
technology is used in animal farming
is in the addition of human genes to
the genes of farm animals to
produce human proteins in milk.
 This is used for complex human
proteins that cannot be made by
bacteria through gene technology.
 The human proteins are extracted
from the animal’s milk and sold for
pharmaceutical purposes. These
animals are called transgenic animals
because they have human DNA in
their cells.
11/7/2009
Making Medically Useful Proteins: Cloning
 More recently, scientists have
turned to cloning animals as a way
of creating identical animals that
can make medically useful
proteins.
 In cloning, the intact nucleus of
an embryonic or fetal cell is
placed into a new egg whose
nucleus has been removed.
 The egg with the new nucleus is
than placed into the uterus of a
surrogate mother and is allowed
to develop.
11/7/2009
Making Medically Useful Proteins: Cloning
 Cloning from Adult Animals:
 In 1997, the first successful
cloning using differentiated cells
from an adult animal resulted in a
cloned sheep named Dolly.
 A differentiated cell is a cell that
has become specialized to become
a specific type of cell.
 In Dolly’s case; a lamb was cloned
from the nucleus of a mammary
cell taken from an adult sheep.
Scientists thought that a
differentiated cell would NOT
give rise to an entire animal. The
cloning of Dolly successfully
proved otherwise.
11/7/2009
Making Medically Useful Proteins: Cloning
 An electric shock was used to
fuse mammary cells from one
sheep with egg cells without
nuclei from another sheep.
 The fused cells divided to form
embryos, which were implanted
into surrogate mothers. Only one
embryo survived the cloning
process.
 Born July 5, 1996; Dolly was the
first cloned sheep, genetically
identical to the sheep that had
provided the mammary cell.
11/7/2009
Problems with Cloning:
 Since Dolly’s birth in 1996,
scientists have successfully
cloned several animals.
 Only a few of these cloned
animals survive however. Many
become fatally oversized.
 Others encounter problems in
development. For example, three
cloned calves were born in March
2001, only to die a month later
from immune system failure.
11/7/2009
The Importance of Genomic Imprinting
 Technical problems with
reproductive cloning lie within a
developmental process that
conditions egg and sperm so that
the “right combination of genes”
are turned “on” or “off” during
early stages of development.
 When cloned offspring become
adults, a different combination of
genes is activated.
 The process of conditioning the
DNA during an early stage of
development is called genomic
imprinting.
11/7/2009
The Importance of Genomic Imprinting
 In genomic imprinting, chemical
changes made to DNA prevent a
gene’s expression without altering
it’s sequence.
 Usually, a gene is locked into the
“off” position by adding methyl
groups to it’s cytosine
nucleotides.
 The bulky methyl groups prevent
polymerase enzymes from reading
the gene, so the gene cannot be
transcribed.
 Later in development, the methyl
groups are removed and the gene
is11/7/2009
reactivated.
Why Cloning Fails:
 Normal vertebrae development
depends on precise genomic
imprinting.
 This process, which takes place in
adult reproductive tissue, takes
months for sperm and years for
eggs.
 Reproductive cloning fails
because the reconstituted egg
begins to divide within minutes.
There is simply not enough time in
these few minutes for the
reprogramming to process
properly.
11/7/2009
Why Cloning Fails:
 Gene keys fail to become properly
methylated, and this leads to
critical problems in development.
 Because of these technical
problems; and because of ethical
problems, efforts to clone
humans are illegal in most
countries.
11/7/2009
11/7/2009