Download Applications of Genetic Engineering

Genetic Engineering
Georgia Performance Standards:
• Examine the use of DNA technology in
forensics, medicine, and agriculture
Essential Questions:
• Should
there be limits on how DNA technology is used?
• How is DNA technology applied to solving problems?
Student Outcomes:
• How DNA comparison is used in forensic
science
• The process of genetic engineering through the
use of recombinant DNA
• Examine and question complex bioethical
issues involving the use of DNA technology in
modern medicine, industry, agriculture and
forensics
Warm-up:
• A New Breed
• The tomatoes in your salad and the dog in your
backyard are a result of selective breeding.
• Over thousands of years, humans have
developed breeds of animals and plants that
have desirable characteristics.
• How do breeders predict the results of crossing
individuals with different traits?
Warm-up:
1. Think of two very different breeds of dogs that are
familiar to you. On a sheet of paper, construct a
table that has the following three heads: the name
of each of the two dog breeds, and “Cross-Breed.”
2. The rows of the table should be labeled with
characteristics found in both breeds of dogs.
Examples might include size, color, type of coat,
intelligence, aggression, and so on.
3. Fill in the column for each of the two dog breeds. In
the column labeled “Cross-Breed,” write in the
characteristic you would expect to see in a cross
between the two breeds you have selected.
Selective Breeding
• Selective Breeding- a method of
improving a species by allowing only those
individual organisms with desired
characteristics to produce the next
generation
– Hybridization
– Inbreeding
Hybridization:
• Hybridization is a breeding technique that
involves crossing different individuals to
bring together the best traits of both
organisms
– Ex: combining the disease resistance of one
plant with the food-producing capacity of
another produces a hardier plant that
increased food supply.
Inbreeding
• Inbreeding is the continued breeding of
individuals with similar characteristics.
• Used to maintain desired characteristics
• Inbreeding helps to ensure that the
characteristics that make each breed unique will
be preserved.
• Risks: Most of the members of a breed are
genetically similar and genetic defects can arise.
Concept Map
Selective Breeding
consists of
Inbreeding
Hybridization
which crosses
which crosses
Similar
Organisms
for
example
Organism
breed A
which
Retains desired
characteristics
Dissimilar
Organisms
for
example
Organism
breed B
Organism
breed A
which
Combines desired
characteristics
Increasing Variation
• Sometimes breeders want more variation
than exists in nature.
• Breeders can increase the genetic
variation in a population by inducing
mutations, which are the ultimate source
of genetic variability.
– Radiation
– Chemicals
Plant Breeding
• Drugs used in plant breeding sometimes cause
plants to produce cells that have double or triple
the normal number of chromosomes.
• Plants grown from such cells are called
polyploid because they have many sets of
chromosomes.
• Polyploidy produces larger and stronger
plants, which increase the food supply for
humans.
Checkpoint Questions:
1. Give one example of selective breeding.
2. Relate genetic variation and mutations to each
other.
3. How might a breeder induce mutations?
4. What is polyploidy?
5. Suggest ways that plants could be altered to
improve the world’s food supply.
Manipulating DNA:
• How are changes made to DNA?
• Scientists use their knowledge of the
structure of DNA and its chemical properties
to study and change DNA molecules.
• Different techniques are used:
–
–
–
–
to extract DNA from cells
to cut DNA into smaller pieces
to identify the sequence of bases in a DNA molecule
to make unlimited copies of DNA.
Genetic engineering
• Genetic Engineering - making changes in
the DNA code of a living organism.
– Process:
• DNA extraction
• Cutting DNA
• Separating DNA
• Reading the sequence
• Cutting and pasting
• Making copies
Molecular
Biology
DNA Extraction
• How do biologists get DNA out of a cell?
• DNA can be extracted from most cells by
a simple chemical procedure:
– The cells are opened and the DNA is
separated from the other cell parts.
Cutting DNA
• DNA molecules from most organisms are
much too large to be analyzed, so
biologists cut them precisely into smaller
fragments using restriction enzymes.
• Restriction enzymes cut DNA at a
specific sequence of nucleotides.
– Very precise
Restriction Enzymes
•This drawing shows how
restriction enzymes are
used to edit DNA.
•The restriction enzyme
EcoRI, for example, finds
the sequence CTTAAG
on DNA.
•Then, the enzyme cuts
the molecule at each
occurrence of CTTAAG.
VIDEO
•Different restriction
enzymes recognize and
cut different sequences of
nucleotides on DNA
molecules.
Separating DNA
• In gel electrophoresis, a
mixture of DNA fragments
is placed at one end of a
porous gel, and an electric
voltage is applied to the
gel.
• When the power is turned
on, DNA molecules, which
are negatively charged,
move toward the positive
end of the gel.
• The smaller the DNA
fragment, the faster it
moves.
• Uses:
– Comparing
genomes of
different organisms
or individuals.
– Locating and
identifying one
particular gene out
of the millions of
genes in an
individual’s
genome.
Gel Electrophoresis
Power
source
DNA plus
restriction
enzyme
Longer
fragments
Shorter
fragments
Mixture of
DNA
fragments
Gel
Using the Sequence of DNA:
• “Reading” a DNA sequence is now an
automated process.
• The pattern of colored bands
(Fluorescently labeled nucleotides) tells
the exact sequence of bases in the DNA.
• Each color corresponds to a specific
nucleotide base (A, G, C, and T)
DNA Sequencing
Fluorescent Single strand
of DNA
dye
Strand broken
after A
Power
source
Strand broken
after C
Strand broken
after G
Strand broken
after T
Gel
Cutting and Pasting
• Enzymes make it possible to take a gene
from one organism and attach it to the
DNA of another organism.
• Such DNA molecules are sometimes
called recombinant DNA because they
are produced by combining DNA from
different sources.
Making Copies
• In order to study
genes, biologists
often need to make
many copies of a
particular gene.
• A technique known as
polymerase chain
reaction (PCR)
allows biologists to
make copies of DNA.
– PCR Process:
1. DNA is heated to
separate strands
2. DNA is cooled to
allow primers to
bind
3. DNA polymerase
copies the strands
PCR:
Polymerase Chain
Reaction
VIDEO
Checkpoint Questions:
1.
Describe the process scientists use to manipulate DNA.
2.
Why might a scientist want to know the sequence of a
DNA molecule?
3. How does gel electrophoresis work?
4. Which technique can be used to make multiple copies of
a gene? What are the basic steps in this procedure?
5. How is genetic engineering like computer programming?
Cell Transformation
– During Cell Transformation, a cell takes in
DNA from outside the cell.
• Plant and animal
– This external DNA becomes a part of the cell’s
DNA.
• One way to make recombinant DNA is to
insert a human gene into bacterial DNA.
• The new combination of genes is then
returned to a bacterial cell, and the bacteria
can produce the human protein.
• video
Transforming Bacteria
• Recombinant DNA is used.
• The foreign DNA is first joined to a small,
circular DNA molecule known as a
plasmid.
– Plasmids have a DNA sequence that serves
as a bacterial origin of replication.
– Plasmids have a genetic marker—a gene
that makes it possible to distinguish bacteria
that carry the plasmid from those that don’t.
Transforming Bacteria
Plant Cell Transformation
• Recombinant plasmids can be used to infect
plant cells.
• DNA can also be injected directly into some
plant cells.
• Cells transformed by either procedure can be
cultured to produce adult plants.
•
Plant Cell Transformation
Gene to be
transferred
Agrobacterium
tumefaciens
Cellular
DNA
Inside plant cell,
Agrobacterium inserts
part of its DNA into host
cell chromosome
Recombinant
plasmid
Plant cell
colonies
Transformed bacteria
introduce plasmids into
plant cells
Complete plant is
generated from
transformed cell
Animal Cell Transformation:
Knockout Genes
• Recombinant DNA can replace a gene in an
animal’s genome.
• The ends of the recombinant DNA recombine
with sequences in the host cell DNA.
• When the recombinant DNA is inserted into
the target location, the host cell’s original
gene is lost or knocked out of its place.
Knockout Genes
Checkpoint Questions:
1. What is transformation?
2. How can you tell if a transformation experiment
has been successful?
3. How are genetic markers related to
transformation?
4. What are two features that make plasmids
useful for transforming cells?
5. Compare the transformation of a prokaryotic cell
with the transformation of a eukaryotic cell.
Applications of Genetic Engineering
• Scientists have developed many
transgenic organisms, which are
organisms that contain genes from other
organisms.
– scientists have removed a gene for green
fluorescent protein from a jellyfish and tried to
insert it into a monkey.
Applications of Genetic Engineering
•
Transgenic animals are often used in
research.
–
•
What might be the benefit to medical research of a
mouse whose immune system is genetically altered
to mimic some aspect of the human immune
system?
Transgenic plants and animals may have
increased value as food sources.
–
What might happen to native species if transgenic
animals or plants were released into the wild?
Transgenic Organisms:
• The universal nature of genetic mechanisms
makes it possible to construct organisms that
are transgenic, meaning that they contain
genes from other organisms.
• A gene from one organism can be inserted
into cells from another organism.
• These transformed cells can then be used to
grow new organisms.
Transgenic Bacteria or Yeast:
• Transgenic bacteria reproduce rapidly and
are easy to grow.
• Therefore they now produce a host of
important substances useful for health and
industry.
– human insulin, growth hormone, and
clotting factor
Transgenic Animals:
• Transgenic animals have been used to study genes and to
improve the food supply
– Strains of mice
• produced with human genes that make their immune
systems act similarly to those of humans.
• study the effects of diseases on the human immune
system.
– Transgenic livestock
• produced with extra copies of growth hormone genes.
• such animals grow faster and produce meat that is less
fatty than that from ordinary animals.
– Transgenic chickens
• resistant to the bacterial infections that sometimes
cause food poisoning.
Transgenic Plants:
• Transgenic plants help
to increase our food
supply.
• Genes produce a natural
insecticide (this avoids
synthetic pesticide use).
• Genes that enable them
to resist weed-killing
chemicals (allows farmers
to grow more food by
controlling weeds.
• Human antibodies
that can be used to
fight disease;
• Plastics that can now
be produced only
from petroleum
• Foods that are
resistant to rot and
spoilage.
Cloning:
• A clone is a member of a population of
genetically identical cells produced from a
single cell.
• Cloned colonies of bacteria and other
microorganisms are easy to grow, but this
is not always true of multicellular
organisms, especially animals.
Cloning:
• Clones are used for medical and
scientific value, but also causes ethical
issues.
• In 1997, Scottish scientist Ian Wilmut
stunned biologists by announcing that he
had cloned a sheep
Cloning
A body cell is taken from a donor animal.
An egg cell is taken from a donor animal.
The nucleus is removed from the egg.
The body cell and egg are fused by electric shock.
The fused cell begins dividing, becoming an embryo.
The embryo is implanted into the uterus of a foster mother.
The embryo develops into a cloned animal.
Cloning of the First Mammal
Section 13-4
A donor cell is taken from
a sheep’s udder.
Donor
Nucleus
These two cells are fused
using an electric shock.
Fused Cell
Egg Cell
The nucleus of the
egg cell is removed.
An egg cell is taken
from an adult
female sheep.
Embryo
Cloned Lamb
The embryo
develops normally
into a lamb—Dolly
Go to
Section:
The fused cell
begins dividing
normally.
Foster
Mother
The embryo is placed
in the uterus of a foster
mother.
Checkpoint Questions:
1. List one practical application for each of the
following: transgenic bacteria, transgenic
animals, transgenic plants.
2. What is a transgenic organism?
3. What basic steps were followed to produce
Dolly?
4. List reasons you would or would not be
concerned about eating genetically modified
food.
Warm-up:
• As you become more aware of scientific
advances in genetics, you might realize that with
the ability to manipulate genes, there comes
responsibility.
• This ability provides an opportunity to improve
the lives of many people.
• But there is also a potential for errors or
intentional misuse of the technology.
Warm-up:
Working with a partner, answer the following
questions.
1. In what type of situation do you think genetic
engineering—changing the genes of organisms—is
warranted? Explain your reasoning about your
position. If you do not think that genetic engineering
is ever warranted, explain your reasons for your
position.
2. In what type of situation do you think genetic
engineering might be misused? Suggest limits that
might be placed on the manipulation of genes to
avoid its misuse.
DNA fingerprinting
• Analysis of sections of DNA that have little
or no known function, but vary widely from
one individual to another, in order to
identify individuals
• The reliability of DNA evidence has
helped convict criminals as well as
overturn many convictions.
Figure 14-18 DNA Fingerprinting
Section 14-3
Restriction enzyme
Go to
Section:
Chromosomes
contain large
amounts of DNA
called repeats that
do not code for
proteins. This
DNA varies from
person to person.
Here, one sample
has 12 repeats
between genes A
and B, while the
second sample
has 9 repeats.
Restriction
enzymes are used
to cut the DNA
into fragments
containing genes
and repeats. Note
that the repeat
fragments from
these two samples
are of different
lengths.
The DNA fragments
are separated
according to size
using gel
electrophoresis.
The fragments
containing repeats
are then labeled
using radioactive
probes. This
produces a series of
bands—the DNA
fingerprint.
The Human Genome Project:
• The Human Genome Project is an attempt
to sequence all human DNA.
• VIDEO
Gene Therapy
• Curing genetic disorders by gene therapy.
• Gene therapy is the process of changing the
gene that causes a genetic disorder.
• In gene therapy, an absent or faulty gene is
replaced by a normal, working gene.
• This way, the body can make the correct protein
or enzyme it needs, which eliminates the cause
of the disorder.
Figure 14-21 Gene Therapy
Section 14-3
Bone
marrow cell
Normal hemoglobin gene
Nucleus
Chromosomes
Genetically engineered virus
Go to
Section:
Bone
marrow
Think About It…
• What will happen to the human species if
we gain the opportunity to design our
bodies…
Checkpoint Questions:
1. What is the Human Genome Project?
2.
Describe how gene therapy works.
3. Name two common uses for DNA testing.
4. Describe how molecular biologists identify genes in
sequences of DNA.
5. Do you think it should be legal for people to use genetic
engineering to affect their children’s characteristics?
Give reasons for your answer.