Download Genetic Engineering

DNA Technology &
Genetic Engineering
Georgia Performance Standards:
• Examine the use of DNA technology in
forensics, medicine, and agriculture.
Essential Questions:
• How
are genetically modified plants and animals made
and used in medicine and agriculture?
• How is DNA technology applied to solving problems?
Selective Breeding
• Selective Breeding- a method of
improving a species by allowing only those
individual organisms with desired
characteristics to produce to 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 Cut DNA
•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 Separates DNA
Power
source
DNA plus
restriction
enzyme
Longer
fragments
Shorter
fragments
Mixture of
DNA
fragments
Gel
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 makes
copies of DNA
DNA fingerprinting
• The pattern that results from gel
electrophoresis is known as as DNA finger
print.
• The more similar the DNA fingerprints
of two organisms, the more recently
they shared a common ancestor.
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.
- The technicians
place a DNA
fingerprint from a
known person
next to a DNA
fingerprint found
at the scene of
the crime.
- If the DNA
fingerprints
match, the
person can be
placed at the
scene of the
crime.
-It is easy to see in this
example that daughter 2 is the
child from the mother’s
previous marriage and son 2 is
adopted.
-You can see that both
daughter 1 and son 1 share
RFLPs with both the mom and
dad (colored blue and yellow
respectively), while daughter 2
has RFLPs of the mom but not
the dad, and son 2 does not
have RFLPs from either
parent.
- Even if the RFLPs were not
color coded, you could still
distinguish the parents of the
children by looking at the
position of the bands in the
agarose gel. In reality, all of the
bands look the same and only
the positions are different.
Chapter
13
Genetics and Biotechnology
13.2 DNA Technology
 To understand how DNA is sequenced, scientists mix an
unknown DNA fragment, DNA polymerase, and the four
nucleotides—A, C, G, T in a tube.
Chapter
13
Genetics and Biotechnology
13.2 DNA Technology
 Each nucleotide is
tagged with a
different color of
fluorescent dye.
 Every time a
modified
fluorescent-tagged
nucleotide is
incorporated into the newly synthesized strand,
the reaction stops.
Chapter
13
Genetics and Biotechnology
13.2 DNA Technology
 The sequencing reaction is complete when the
tagged DNA fragments are separated by gel
electrophoresis.
Reading a DNA Sequence
Figure 22.3
Deriving a DNA Sequence
Figure 22.4
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
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.
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
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.
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
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.