Download Ch. 13 Genetic Engineering

Ch. 13 Genetic Engineering
Ch. 13 Outline

13-1: Changing the Living World
Selective Breeding
 Increasing Variation
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13-2: Manipulating DNA
The Tools of Molecular Biology
 Using the DNA Sequence

Ch. 13 Outline
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13-3: Cell Transformation
Transforming Bacteria
 Transforming Plant Cells
 Transforming Animal Cells
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13-4: Applications of Genetic Engineering
Transgenic Organisms
 Cloning
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What is genetic engineering?

In 1973, Mr. Cohen and Mr. Boyer
conducted an experiment on the DNA of
an American frog. They found and
isolated the gene that codes for ribosomal
RNA in the DNA of the frog. They
removed that gene from the frog and
inserted it into some E. Coli Bacteria.
What Happened?

During transcription, the bacteria then
produced the frog RNA!
Genetic Engineering: the process of
manipulating (moving) genes for practical
purposes (useful)
 Recombinant DNA: DNA made from 2 or
more organisms that are different.

The Basic Steps of Genetic
Engineering
1.
Cutting the DNA:
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Restriction Enzymes: bacterial enzymes that
recognize and bind to specific short
sequences of DNA, and then cute the DNA
between specific nucleotides within the
sequences.
Vector: agent used to carry the gene of
interest – usually plasmids

Plasmid: the circular DNA molecules that
replicate
The Basic Steps to Genetic
Engineering
2.
Making Recombinant DNA
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3.
DNA fragments of interest (that have already
been cut) are combined with the vector.
DNA ligase – the enzyme bonds the 2 ends
of the fragments to the vectors.
Cloning

Gene cloning: the process of making many
copies of a gene

Bacteria reproduce by binary fission
The Basic Steps to Genetic
Engineering
4.
Screening

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Cells that have received the gene of interest
are separated out.
Those cells then continue to produce the
protein coded for by the gene
Cutting DNA & Making
Recombinant DNA

How Restriction enzymes work:


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The Enzymes recognize specific sequences on
Human and Bacterial Plasmids
The Enzymes cut the strands.
The cut produces DNA fragments with short strands
on each end that are complementary to each other


“Sticky Ends”
Both the human DNA and the Plasmid “Open Up”
with the same sticky ends remaining

They Bind Together
Diagram
Recognition sequences
DNA sequence
Recognition sequences
DNA sequence
Restriction enzyme
EcoRI cuts the DNA
into fragments.
Sticky end
Confirmation of a Cloned Gene

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One method used identify a specific
gene is called a Southern Blot
Steps:
1.
2.
Cut DNA from bacteria with restriction
enzymes.
DNA fragments are separated by a gel
soaked in a chemical solution.

Gel electrophoresis – uses an electric field
within a gel to separate molecules by their size
Confirmation of a Cloned Gene

Negatively charged DNA is put into these
wells.


They are attracted to the positive pole from
the electric field.
The Smallest DNA fragments move the
fastest
Gel Electrophoresis
Power
source
DNA plus restriction
enzyme
Longer
fragments
Shorter
fragments
Mixture of DNA
fragments
Gel
Confirmation of a Cloned Gene
3.
The DNA separated is then transferred to
a filter paper (blotted) and a probe
solution is added.

4.
Probes: radioactive RNA or single-stranded
DNA pieces that are complementary to the
gene of interest
Only DNA fragments complementary to
the probe will form and bind bands
Confirmation of Cloned Genes

Why do this?

Bacterial colonies can be used to produce
large quantities of the protein (used to study
or make drugs)
Genetically engineered Drugs and
Vaccines
Today, many pharmaceutical companies
around the world produce important
proteins using genetic engineering.
 Vaccine: a solution containing all or part of
a harmless version of a pathogen; used to
prevent viral diseases (don’t respond to
drugs)
 Many vaccines are made using genetic
engineering

DNA fingerprinting
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DNA fingerprinting: a pattern of dark bands on
photographic film that is made when an
individuals DNA restriction fragments are
separated by gel electrophoresis, probed, and
exposed to X-ray film.
DNA fingerprints can be used to establish
paternity, identify genetic disorders, or in
forensics (scientific study of cause of injury or
death in criminal activity)
Improving Crops

Genetic engineers can add favorable
characteristics to a plant

Resistant to insects (no longer need
pesticides); resistant to weed killer (so crops
won’t die, but weeds will); improved nutrition –
rice + corn
Plant Transformation
Agrobacterium
tumefaciens
Gene to be
transferred
Cellular
DNA
Recombinant
plasmid
Inside plant cell,
Agrobacterium inserts part of
its DNA into host cell
chromosome
Plant cell colonies
Transformed bacteria introduce
plasmids into plant cells
Complete plant is
generated from
transformed cell
Animal Farming
Growth hormones given to cows to
produce more milk
 Human genes added to farm animals in
order to have human proteins in their milk

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The Human proteins are extracted from milk
and sold to pharmacy companies.
 Useful
for complex proteins that can’t be made in
bacteria
Creating HGH
Recombinant
DNA
Gene for human
growth hormone
Gene for human
growth hormone
Human Cell
Sticky
ends
DNA
recombination
DNA
insertion
Bacterial Cell
Bacterial
chromosome
Plasmid
Bacterial cell for
containing gene for
human growth hormone
Animal Farming

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Transgenic animals: Animals that have foreign
DNA in their cells
Cloning of animals is another way to make large
quantities of a certain protein.
How it works: an intact nucleus from an
embryonic cell (whose DNA has recombined
with a human gene) is placed into an egg whose
nucleus has been removed. The “new” egg is
then placed into the uterus of an animal.
Cloning
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.
The fused cell
begins dividing
normally.
Embryo
Cloned Lamb
The embryo
develops normally
into a lamb—Dolly
Foster
Mother
The embryo is placed
in the uterus of a foster
mother.