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Guided Notes on Chapter 11 – Gene Technology
Section 1: Genetic Engineering
Objectives
 Describe four basic steps commonly used in genetic engineering experiments.
 Evaluate how restriction enzymes and the antibiotic tetracycline are used in genetic
engineering.
 Relate the role of electrophoresis and probes in identifying a specific gene.
Basic Steps of Genetic Engineering

The process of manipulating genes for practical purposes is called genetic
engineering.

Genetic engineering may involve building recombinant DNA — DNA made from two or
more different organisms.
Steps in a Genetic Engineering Experiment ----See figure 2 page 229

Genetic engineering experiments use different approaches, but most share four basic
steps:

Step 1: The DNA from the organism containing the gene of interest is cut by restriction
enzymes. Restriction enzymes are bacterial enzymes that recognize and bind to
specific short sequences of DNA, and then cut the DNA between specific nucleotides
within the sequences. The DNA from a vector also is cut. A vector is an agent that is
used to carry the gene of interest into another cell. Commonly used vectors include
viruses, yeast, and plasmids, circular DNA molecules that can replicate independently
of the main chromosomes of bacteria.
Original Bacterium
Cloning Vector
Gene Clones
Step 2: Recombinant DNA is produced.
Step 3: In a process called gene cloning, many copies of the gene of interest are
made each time the host cell reproduces.
Step 4: Cells undergo selection and then are screened.
(video clip) How do they separate the cells with the gene of interest from those without?
The vector contains a gene that allows the bacteria to survive a particular antibiotic. When the
antibiotic is added, only those cells with the gene of interest survive.
Using Plasmids to Produce Insulin (Video clip)
What do they use to isolate a specific gene from human DNA? Restriction enzyme
Since the plasmid is also cut with the same restriction enzyme, both the gene and the plasmid
have complimentary sticky ends.
Cutting DNA and Making Recombinant DNA

Restriction enzymes recognize a specific sequence of DNA.

The cuts of most restriction enzymes produce pieces of DNA with short single strands on
each end that are complementary to each other. The ends are called sticky ends.

The two DNA molecules bond together by means of complementary base pairing at the
sticky ends.
Restriction Enzymes Cut DNA ----See book figure 3 page 230
Action of Restriction Enzymes (Video clip)
What purpose do the sticky ends formed by restriction enzymes serve? They allow scientists to
combine DNA from different sources provided they have been cut by the same restriction
enzyme.
Cloning, Selecting, and Screening Cells

One difficult part in a genetic engineering experiment is finding and isolating the cells
that contain the gene of interest.

First, the cells that have taken up the plasmid must be identified.

Often vectors include genes for resistance to certain kinds of antibiotics. This resistance
helps scientists identify the cells of interest.
Confirmation of a Cloned Gene

One method used to identify a specific gene is a technique called a Southern blot, which
has four steps:
Step 1: In a Southern blot, the DNA from each bacterial clone colony is isolated and cut
into fragments by restriction enzymes.
Step 2: The DNA fragments are separated by gel electrophoresis, a technique that
uses an electric field within a gel to separate molecules by their size.
Step 3: The DNA bands are then transferred (blotted) directly onto a piece of filter
paper, which is moistened with a probe solution. Probes are radioactive- or fluorescentlabeled RNA or single-stranded DNA pieces that are complementary to the gene of
interest.
Step 4: Only the DNA fragments complementary to the probe will bind with the probe
and form visible bands.
Gel Electrophoresis
For what purpose is gel electrophoresis used? It’s used to separate fragments of DNA
molecules, which are used to make DNA fingerprints.
Section 2: Human Application of Genetic Engineering
Objectives
 Summarize two major goals of the Human Genome Project.
 Describe how drugs produced by genetic engineering are being used.
 Summarize the steps involved in making a genetically engineered vaccine.
 Identify two different uses for DNA fingerprints.
The Human Genome Project

In February of 2001, scientists working on the Human Genome Project published a
working draft of the human genome sequence.

The sequence of an organism’s genome is the identification of all base pairs that
compose the DNA of the organism.

The Human Genome Project is a research project that has linked over 20 scientific
laboratories in six countries.
The Geography of the Genome
 Only 1 to 1.5 percent of the human genome is DNA that codes for proteins.

Each human cell contains about six feet of DNA, but less than 1 inch of that is devoted
to exons.

Exons are scattered about the human genome in clumps that are not spread evenly
among chromosomes.
The Number of Human Genes
 Human cells contain only about 30,000 to 40,000 genes.

This is only about double the number of genes in a fruit fly.
Genetically Engineered Drugs and Vaccines
Drugs

Many genetic disorders and other human illnesses occur when the body fails to make
critical proteins.

Today hundreds of pharmaceutical companies around the world produce medically
important proteins in bacteria using genetic engineering techniques.

Factor VIII, a protein that promotes blood clotting, is an example of a GM medicine
(genetically modified; a drug manufactured by genetic engineering).
Vaccines

A vaccine is a solution containing all or part of a harmless version of a pathogen
(disease-causing microorganism).

When a vaccine is injected, the immune system recognizes the pathogen’s surface
proteins and responds by making defensive proteins called antibodies.

In the future, if the same pathogen enters the body, the antibodies are there to combat
the pathogen and stop its growth before it can cause disease.
Vaccine (Video clip)
Vaccines take advantage of the body’s immune response.
Vaccines

Traditionally, vaccines have been prepared either by killing a specific pathogenic
microbe or by making the microbe unable to grow.

The problem with this approach is that there is a small but real danger that a failure in
the process to kill or weaken a pathogen will result in the transmission of the disease to
the very patients seeking protection.

Vaccines made by genetic engineering techniques avoid the dangers of a traditional
vaccine.
DNA Fingerprinting

Other than identical twins, no two individuals have the same genetic material.

A DNA fingerprint is a pattern of dark bands on photographic film that is made when an
individual’s DNA restriction fragments are separated by gel electrophoresis, probed, and
then exposed to an X-ray film.

Because it can be performed on a sample of DNA found in blood, semen, bone, or hair,
DNA fingerprinting is useful in forensics.
DNA Fingerprint
Name 3 things for which a DNA fingerprint can be used.
1. To compare DNA from more that 1 person to establish whether they are related.
2. To identify genes that cause genetic disorders.
3. To help solve crimes.
Making a DNA Fingerprint (Video clip)

Restriction fragment length polymorphism, or RFLP, analysis is the technique used to
prepare DNA fingerprints.
1. DNA is digested with restriction enzymes.
2. This results in fragments of different lengths. Each person has a different pattern
of fragment lengths.
3. Fragments are separated by gel electrophoresis. Shorter fragments travel farther.
4. The fragments are transferred to special paper and mixed with radioactive
probes. The probes create a pattern when exposed to film. Every person’s DNA
results in a different pattern.