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TEACHER’S GUIDE
TEACHER’S GUIDE
clones — Genetically identical organisms, or identical segments of DNA.
luminescence — The emission of light at low temperatures.
standard “ladder” — DNA of a specific, predetermined size from a
• gslc.genetics.utah.edu/
An online genetics curriculum developed by The Genetic Science Learning
Center that includes detailed classroom activities.
• vector.cshl.org/dnaftb/1/concept/index.html
“DNA From the Beginning” is an animated primer on the basics of DNA,
genes and heredity.
known source, digested with a restriction enzyme that cuts that piece of
DNA a known number of times, yielding a predicted number of bands
whose sizes are known exactly.
“heat-shock” — A marked temperature change that is thought to induce
bacteria cells to readily absorb plasmid DNA.
restriction endonucleases — Special enzymes that cut or cleave DNA
molecules at specific sites.
ligase — An enzyme capable of fusing two ends of a DNA molecule.
DNA sequencing — Determining the exact order of base pairs in a DNA
segment.
TEACHER’S GUIDE
Suggested Print Resources
• Coen, Enrico. Art of Genes: How Organisms Make Themselves. Oxford
Press, New York, NY; 2000.
• Maddox, Brenda. Rosalind Franklin: And the Discovery of the Double
Helix Structure of DNA. Harper Collins, New York, NY; 2002.
• Richardson, Hazel. How to Clone A Sheep. Franklin Watts, New York, NY;
2001.
DNA TRANSFORMATION
Follow-up Activities
• Direct students to prepare an informational pamphlet of a human
genetic condition, making sure to include symptoms of the disease,
genetic cause of the disease, diagnostic testing available, information on
types of inheritance, populations (ancestral groups) in which this
disease is most common, recent research or development, and other
relevant information.
• Instead of using bacteria, some DNA fragments can be copied millions of
times under the right conditions by mixing short segments of DNA, free
nucleotides, and enzymes.This method is called the polymerase chain
reaction, or PCR. Have students research the development of this
technique.
• Have students research the role of bioethics in genetic research and
debate an issue such as human cloning or the concept of patenting
genes. Insist that they gather data to support their argument.
Suggested Internet Resources
Periodically, Internet Resources are updated on our Web site at
www.LibraryVideo.com
• www.biotech.iastate.edu/Educational_resources.html
This site from the Biotechnology Outreach Education Center at Iowa
State University contains a wealth of information about biotechnology,
including classroom lab activities, career information and bioethics case
studies.A protocol for the transformation of bacteria with a luminescent
gene is included.
• www.accessexcellence.org/
A excellent compendium of biotechnology articles, exercises, current
bioscience news, and other information designed for biology teachers
and students.
(Continued)
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Grades 9–12
I
TEACHER’S GUIDE CONSULTANTS
Dr. Robert Orr
Professor of Chemistry
Delaware Valley College of Science & Agriculture
Paula J. Bense, M.Ed.
Schlessinger Media
Curriculum Specialist
COMPLETE LIST OF TITLES
• CHROMATOGRAPHY
• COMPARATIVE ANATOMY:
DISSECTION
• DNA TRANSFORMATION
• ENERGY & CHEMICAL
REACTIONS
• LAB SAFETY
Teacher’s Guides Included
and Available Online at:
• THE LAWS OF MOTION:
HOVERCRAFTS
• PROPERTIES OF GASES
• SPECTROPHOTOMETRY
• TITRATION
• WATER ANALYSIS
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Teacher’s Guide and Program Copyright 2003 by Schlessinger Media,
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Produced and directed by PhotoSynthesis Productions, Inc.
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All rights reserved.
nstruction in both scientific ideas and processes is
necessary for students to have a well-balanced
science education. By practicing the skills of science
while solving everyday problems, students will learn to
raise good questions and find accurate answers about
the objects, forces and organisms in their world.
Inquiry-based teaching and learning goes well beyond
the traditional scientific method to focus not only on
engaging students in the “doing” of science, but in
thinking of science as an active process that allows
them to focus on their own questions as they develop
the ability to plan and execute a scientific investigation.
Students’ ability to use a variety of technologies should
be an integral component of all scientific investigations.
Mathematics should also play a role in all aspects of scientific inquiry. Students find that these skills empower
them to engage in problem solving in all areas of their
lives.
At various points throughout the video, there are
opportunities for the educator to actively involve students in the topic by recreating the investigations or
expanding upon the onscreen discussion.
Program Summary
Genes, found in chromosomes, are pieces of DNA that control the traits an
organism possesses and the proteins it produces.The structure of the DNA
molecule itself is identical among all living things — it is made up of a series
of units called nucleotides, each consisting of a sugar called deoxyribose, a
phosphate group, and one of four nitrogenous bases: adenine (A), thymine
(T), guanine (G), or cytosine (C).The four bases are paired on the DNA molecule in a very specific way: A always with T and G always with C.These bases
are joined by relatively weak hydrogen bonds, allowing them to “unzip” when
necessary.The alternating sugar and phosphate units form the backbone of a
structure that resembles a twisted ladder known as a double helix.
Bacteria, such as E. coli, have genes on a chromosome, as well as a small circular piece of DNA called a plasmid. Because of its size and properties, a
plasmid is able to pass freely from one cell to another, making it a perfect
vehicle, or vector, for transporting DNA. A gene responsible for a specific
physical trait can be inserted into the plasmid and then transferred into bacteria by a process known as transformation.A successful transformation will
produce millions of identical bacteria cells, called clones, along with the
desired gene product.
Molecular biologists are able to cut DNA fragments out of one organism and
paste them into another using a toolkit of enzymes. Restriction endonucleases are used as molecular scissors, cutting DNA at specific recognition
sequences of nucleotides. Each restriction enzyme requires specific reaction
conditions to work optimally.After DNA is cut, the fragment of interest can
be isolated through a technique known as gel electrophoresis.
Gel electrophoresis, a technique widely used in the molecular biology laboratory, is the migration of electrically-charged particles in an electric field.To
create the gel, agarose powder is mixed with a liquid buffer solution and
then dissolved by heating.The solution is poured into a tray containing a
plastic “comb” and allowed to harden.The comb makes wells in the hardening gel into which the DNA samples, along with a colored dye, will be loaded.
The dye helps track the progress of each sample as it travels through the gel
and allows the fragments, which are invisible to the naked eye, to be seen for
analysis.
Students will isolate bacteria and alter the genotype by inserting plasmid
DNA. (The DNA will contain genes that will cause the bacteria to be resistant
to antibiotics and/or glow in the dark.) This will visibly affect the physical
traits (phenotype) of the microorganisms that are successfully transformed.
Students will also become familiar with sterile technique in the laboratory.
Laboratory Investigation
Materials needed:
indelible marker
calcium chloride solution.
ampicillin solution.
plasmid DNA solution.
LB broth solution
Glass spreader
95% ethanol
1.5 mL microcentrifuge tubes
1 petri dish containing colonies of E. coli
sterile inoculating loops
micropipets/tips
4 agar plates
42° C water bath
container of ice
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After donning personal protective equipment (gloves/goggles/labcoat), students label two sterile 1.5 mL microtubes: one +DNA and one –DNA. They
then add 250 µL of cold calcium chloride solution and place the tubes on
ice. Using sterile loops, an isolated colony of E. coli bacteria is selected from
the agar plate for immersion in each microtube. 10 µL plasmid DNA is added
to the +DNA tube and no DNA is added to the –DNA tube.The cells are resuspended in the solution by vigorous mixing and then placed on ice for 15
minutes. (The CaCl2 solution causes the bacterial cell walls to become permeable to the plasmids. Cells are kept cold to prevent them from growing
while the plasmids are being absorbed.) While the tubes are incubating,
LB/Amps plate are labeled +DNA and –DNA. (The +DNA plate will receive
the transformed bacteria, while the –DNA plate will act as a negative
control.) LB plates are labeled the same way. (These plates are positive controls to make sure the bacteria survived the transformation process.)
Students then remove the microtubes from ice and immerse them in a 42°C
water bath for 90 seconds. (This “heat shock” step causes pores in the bacterial membrane to enlarge, allowing the plasmids to enter the cells.) 250 µL of
LB broth (nutrients for the growing bacteria) are added to each tube and the
tubes are tapped to mix the solution.The tubes are then left at room temperature for 5 to 15 minutes.
Using sterile pipets, 100 µL of each solution is transferred to the appropriately labeled plate and spread using a sterile glass spreader. (Sterile technique
is extremely important during this step.) The plates are then incubated at
30°C overnight and can then be examined in a very dark room.
Make sure that all materials contaminated with bacteria are disposed
of properly. Clean up contaminated materials by soaking them in 10%
bleach for 15 minutes or more before washing.
• Information about the preparation and materials necessary to perform this
investigation is available at the following Web site:
http://biotech.biology.arizona.edu/labs/
Bact_glow_tradition_teach.html
Discussion Topics
• Do you think that the transfer of genes across living species should be controlled or even prevented? Why or why not?
• Why is it beneficial to use organisms like bacteria to study genes?
• What is gene therapy?
• Explain why and how gel electrophoresis separates DNA fragments by
length.
• What is a plasmid?
• What are “gene products”?
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Vocabulary
genes — The functional and physical units of heredity passed from parent
to offspring. Genes are pieces of DNA.
chromosome — A rod-like structure of tightly coiled DNA.
deoxyribonucleic acid — The double-stranded molecules inside the
nucleus of a cell that carry the genetic instructions for making living
organisms.
nucleotide — The basic building block of DNA comprised of a molecule
of sugar, a molecule of phosphoric acid, and a molecule called a base.
Groups of three nucleotides, called “codons,” direct a cell to produce a
specific amino acid to form proteins.
base pair — Two nitrogenous bases which form a “rung” of the DNA
ladder. In DNA, adenine (A) always pairs with thymine (T) and guanine (G)
always pairs with cytosine (C).The order in which they link make the two
strands of DNA mirror images of each other.
double helix — The structural arrangement of DNA, which looks something like an immensely long ladder twisted into a helix, or coil.The sides
of the “ladder” are formed by a backbone of sugar and phosphate molecules, and the “rungs” consist of nucleotide bases joined weakly in the
middle by hydrogen bonds.
transformation — A process by which the genetic material carried by
an individual cell is altered by incorporation of DNA from another organism into its genome.This method has been used to produce many pharmaceuticals, such as human insulin.
E. coli -- Common bacterium that has been studied intensively by geneticists because of its small genome size, normal lack of pathogenicity, and
ease of growth in the laboratory.
genome — The entire set of genetic material belonging to an organism.
mutation — A change in the genetic code of an organism. Some mutations may be beneficial for an organism; others may be lethal, but the
majority go unnoticed.
genetic engineering — The process of manufacturing and manipulating
genes under controlled conditions.
gene therapy — A controversial field of research in which genes are
transferred to a recipient in the hope of curing a genetic disorder.
gel electrophoresis — The process in which molecules can be separated according to size and electrical charge by applying an electric
current to them.The current forces the molecules through pores in a thin
layer of a firm jelly-like substance. Smaller fragments usually travel further
than large ones.
plasmid — A circular molecule comprised of DNA that is found in many
bacterial cells. Plasmids vary in size but most are between 1,000 to 25,000
base pairs.
vector — An agent, such as a virus or a small piece of DNA called a
plasmid, that carries a modified or foreign gene. When used in gene
therapy, a vector delivers the desired gene to a target cell. (Continued)
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