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Chapter 9 - Biotechnology
Biotechnologies
• Gel Electrophoresis
• PCR
• Recombinant DNA
• Genetic Engineering
• DNA Sequencing
• Cloning
Gene Cloning
• Isolating a DNA sequence of interest and
making multiple copies of it.
Recombinant DNA
• “Re Combining” DNA from different
sources
The Tools of Molecular Biology
Scientists use different techniques to:
• extract DNA from cells
• cut DNA into smaller pieces
• identify the sequence of bases in a DNA
molecule
• make unlimited copies of DNA
Genetic Engineering Video
In genetic engineering,
biologists make changes
in the DNA code of a
living organism.
–DNA Extraction
•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
•Most DNA molecules are too large to be
analyzed, so biologists cut them into smaller
fragments using restriction
enzymes.
Bacterial Gene Insertion Video
Each restriction enzyme cuts DNA at a specific
sequence of nucleotides.
Recognition sequences
DNA sequence
Restriction enzyme EcoR I cuts
the DNA into fragments
Sticky end
Separating DNA
In gel electrophoresis, DNA fragments are
placed at one end of a porous gel, and an
electric voltage is applied to the gel.
First, restriction
enzymes cut DNA
into fragments.
DNA plus
restriction enzyme
The DNA
fragments are
poured into wells
on a gel.
Mixture of DNA
fragments
Gel Electrophoresis
Gel
An electric
voltage is
applied to the
gel.
The smaller the
DNA fragment,
the faster and
farther it will
move across the
gel.
Power
source
Power
source
Longer
fragments
Shorter
fragments
Gel Electrophoresis
Making Copies
Polymerase chain reaction (PCR) is a technique
that allows biologists to make copies of genes.
Small amounts of DNA can be multiplied
making it easier to analyze.
Made possible by an enzyme found in a
bacterium living in hot springs in Yellowstone
National Park.
PCR Video
Polymerase Chain Reaction (PCR)
DNA heated to
separate strands
DNA polymerase adds
complementary strand
DNA fragment
to be copied
PCR cycles 1
DNA copies 1
2
2
3
4
4
8
5 etc.
16 etc.
Quiz 9-1
Restriction enzymes are used to
a) extract DNA.
b) separate DNA.
c) replicate DNA.
d) cut DNA.
During gel electrophoresis, the smaller the
DNA fragment is, the
a) more quickly it moves.
b) heavier it is.
c) more slowly it moves.
d) darker it stains.
The DNA polymerase enzyme found in
bacteria living in the hot springs of
Yellowstone National Park illustrates
a) the importance of biodiversity to
biotechnology.
b) genetic engineering.
c) the polymerase chain reaction.
d) selective breeding.
A particular restriction enzyme is used to
a) cut DNA at a specific nucleotide
sequence.
b) cut up DNA in random locations.
c) extract DNA from cells.
d) separate negatively charged DNA
molecules.
During gel electrophoresis, DNA
fragments become separated because
a) multiple copies of DNA are made.
b) smaller DNA molecules move faster than
larger fragments.
c) recombinant DNA is formed.
d) DNA molecules are negatively charged.
Transforming - Bacteria
During transformation, a cell takes in DNA
from outside the cell. The external DNA
becomes a component of the cell's DNA.
Foreign DNA is first joined to a small, circular
DNA molecule known as a plasmid.
Plasmids are found naturally in some bacteria
and have been very useful for DNA transfer.
The plasmid has a genetic marker — a gene that
makes it possible to distinguish bacteria that
carry the plasmid (and the foreign DNA) from
those that don't.
RecombinationVideo
Recombinant
DNA
Gene for human
insulin
Gene for human
insulin
Human Cell
Bacterial
chromosome
Sticky
ends
DNA
recombination
DNA
insertion
Bacteria cell
Plasmid
Bacteria cell
containing gene
for human insulin
Transgenic Microorganisms
Transgenic bacteria produce
important substances useful for
health and industry. Transgenic
bacteria have been used to produce:
Insulin, growth hormones, antithrombin III
and tissue plasminogen activator to treat
blood clots, erythropoietin for anemia,
blood clotting factors VIII and IX for
hemophilia, and alpha-1-antitrypsin for
emphysema and cystic fibrosis.1
Producing New Kinds of Bacteria
Alcanivorax borkumensis
Transforming Plant Cells
How can you tell if a
transformation experiment has
been successful?
If transformation is successful, the
recombinant DNA is integrated into one
of the chromosomes of the cell and the
gene product will be expressed.
In nature, a bacterium exists that produces
tumors in plant cells.
Researchers can inactivate the tumorproducing gene found in this bacterium and
insert a piece of foreign DNA into the
plasmid.
The recombinant plasmid can then be used
to infect plant cells.
When their cell walls are removed, plant
cells in culture will sometimes take up
DNA on their own.
DNA can also be injected directly into
some cells.
Cells transformed by either procedure can
be cultured to produce adult plants.
Gene to be
transferred
Agrobacterium
tumefaciens
Inside plant cell,
Agrobacterium
inserts part of its
DNA into host
cell
chromosome.
Cellular
DNA
Recombinant
plasmid
Plant cell
colonies
Transformed bacteria
introduce plasmids into
plant cells.
Complete plant
generated from
transformed cell.
Producing New Kinds of Plants
Mutations in some plant cells produce
cells that have double or triple the normal
number of chromosomes.
This condition, known as polyploidy,
produces new species of plants that are
often larger and stronger than their
diploid relatives.
Polyploidy in animals is usually fatal.
Transgenic Plants
•Transgenic plants are now an
important part of our food
supply.
•Many of these plants contain genes
that produce a natural insecticide,
so plants don’t have to be sprayed
with pesticides and genes for
resistance to RoundUp®
Transforming Animal Cells
•Many egg cells are large enough that
DNA can be directly injected into the
nucleus.
•Enzymes may help to insert the foreign
DNA into the chromosomes of the
injected cell.
•DNA molecules used for transformation
of animal and plant cells contain marker
genes.
DNA molecules can be constructed with
two ends that will sometimes recombine
with specific sequences in the host
chromosome.
The host gene normally found between
those two sequences may be lost or
replaced with a new gene.
Transgenic Organisms
•An organism described
as transgenic, contains
genes from other
species.
How are transgenic
organisms useful to human
beings?
Genetic Engineering Video
Recombinant DNA
Flanking sequences
match host
Recombinant DNA
replaces target gene
Target gene
Modified Host Cell DNA
Transgenic Animals
•Transgenic animals have been used to
study genes and to improve the food
supply.
•Mice have been produced with human
genes that make their immune systems
act similarly to those of humans. This
allows scientists to study the effects of
diseases on the human immune system.
Researchers are trying to
produce transgenic chickens
that will be resistant to the
bacterial infections that can
cause food poisoning.
DNA Sequencing
DNA Sequencing
Cloning
•A clone is a member
of a population of
genetically identical
cells produced from a
single cell.
•In 1997, Ian Wilmut
cloned a sheep called
Dolly.
Cloning Dolly
Donor Nucleus
Fused cell
Egg Cell
Embryo
Cloned
Lamb
Foster Mother
Cloning Dolly
Cloning Dolly
Cloning Dolly
Cloning Dolly
Cloning Dolly
Cloning Dolly
Quiz 9-2
Plasmids can be used to transform
a. plant, animal, and bacterial cells.
b. plant cells only.
c. bacteria only.
d. animal cells only.
A common method of determining whether
bacteria have taken in a recombinant plasmid is
to
a. treat them with an antibiotic.
b. introduce them into animal cells.
c. introduce them into plant cells.
d. mix them with other bacteria that do not have
the plasmid.
Successful transformation of an animal or a
plant cell involves
a. changing the cell’s chromosomes into
plasmids.
b. the integration of recombinant DNA into the
cell’s chromosome.
c. treating the cell with antibiotics.
d. destroying the cell wall in advance.
Insulin-dependent diabetes can now be treated
with insulin produced through the use of
a. transgenic microorganisms.
b. transgenic animals.
c. transgenic plants.
d. transgenic fungi.
In producing a cloned animal, an egg cell is
taken from a female and its nucleus is removed.
A body cell is taken from a male. The clone from
this experiment will
a. look just like the female.
b. resemble neither the male nor the female.
c. have a mixture of characteristics from both
animals.
d. be genetically identical to the male.