CHAPTER 12
DNA Technology
1. DNA technology has quickly revolutionized the field of forensics.
2. Beyond the courtroom, DNA technology is responsible for some of the most remarkable
scientific advances in recent years.
3. DNA technology raises serious social, legal, and ethical issues.
Biology and Society: DNA, Guilt, and Innocence
1. Explain how DNA profiling is used in criminal trials.
Recombinant DNA Technology
2. Explain how recombinant DNA technology can be used to produce useful products.
3. Explain how recombinant DNA techniques are used to mass-produce a protein from an
isolated gene.
4. Explain how genetic engineering is used to produce Humulin, human growth hormone,
erythropoietin, vaccines, crops, and “pharm” animals.
5. Describe the process of cloning genes using plasmids.
6. Explain how the “shotgun” approach produces a genomic library.
7. Explain how restriction enzymes and DNA ligase are used to create recombinant DNA.
DNA Profiling and Forensic Science
8. Describe the many ways that DNA profiling can be used in our society.
9. Explain how the polymerase chain reaction (PCR), short tandem repeat (STR) analysis,
restriction fragment length polymorphism (RFLP), and gel electrophoresis are used in
the process of DNA profiling.
Genomics and Proteomics
10. Describe the types of organisms that have been the subject of recent sequencing efforts.
Explain why these particular organisms have been examined.
11. Describe the goals of the Human Genome Project. Explain why our genome presents a
major challenge.
12. Explain how comparative genomics has been used to investigate acts of bioterrorism,
track the spread of disease, and study evolutionary relationships.
13. Explain why scientists study DNA and proteins to better understand the functioning of
cells and organisms.
Human Gene Therapy
14. Describe the steps used to treat severe combined immunodeficiency disease using
human gene therapy.
Safety and Ethical Issues
15. Describe the potential benefits, risks, and concerns of producing genetically modified
foods.
16. Describe the concerns for the abuse of genetic information and technology as it relates
to human society.
Evolution Connection: Profiling the Y Chromosome
17. Describe the surprising results of DNA profiling of the human Y chromosome.
Key Terms
biotechnology
clone
DNA ligase
DNA profiling
DNA technology
forensics
gel electrophoresis
gene cloning
genetic engineering
genetic marker
genetically modified (GM) organism
genomic library
genomics
human gene therapy
human genome project
nucleic acid probe
plasmid
polymerase chain reaction (PCR)
proteomics
recombinant DNA
repetitive DNA
restriction enzyme
restriction fragments
short tandem repeat (STR)
STR analysis
transgenic organism
vaccine
vector
Word Roots
bio = life (biotechnology: the manipulation of living organisms to perform useful
tasks)
liga = tied (DNA ligase: the enzyme that permanently “pastes” together NA
fragments)
trans = across; genic = producing (transgenic organism: an organism that contains
genes from another organism)
Student Media
Activities
Applications of DNA Technology
Restriction Enzymes
Cloning a Gene in Bacteria
DNA Fingerprinting
Gel Electrophoresis of DNA
Analyzing DNA Fragments Using Gel Electrophoresis
The Human Genome Project: Human Chromosome 17
Making Decisions About DNA Technology: Golden Rice
BLAST Animations
Genetic Recombination in Bacteria
DNA Fingerprinting
Gel Electrophoresis
LabBench
Molecular Biology
MP3 Tutors
DNA Technology
Process of Science
How Can Antibiotic-Resistant Plasmids Transform E. coli?
How Can Gel Electrophoresis Be Used to Analyze DNA?
Videos
Discovery Channel Video: Transgenics
Discovery Channel Video: DNA Forensics
Biotechnology Lab
Relevant Current Issues in Biology Articles
Current Issues in Biology, volume 2 (ISBN 0-8053-7108-7)
Tumor-Busting Viruses
Does Race Exist?
Current Issues in Biology, volume 3 (ISBN 0-8053-7527-9)
Back to the Future of Cereals
Current Issues in Biology, volume 4 (ISBN 0-8053-3566-8)
CSI: Reality
Current Issues in Biology, volume 6 (ISBN 0-321-59849-0)
Diet Advice From DNA
Traces of a Distant Past
Your Cells Are My Cells
Relevant Songs to Play in Class
“Who Are You” (aka theme to the TV show
CSI), The Who
Chapter Guide to Teaching Resources
Recombinant DNA Technology
Student Misconceptions and Concerns
1. The roles of restriction enzymes and nucleic acid probes, as well as many other aspects
of recombinant DNA techniques, rely on a firm and comfortable understanding of basic
molecular genetics. Consider addressing Chapter 12 after an exam that addresses the content
in Chapters 10 and 11.
2.Students might bring some awareness and/or concerns about biotechnology to the
classroom, for example, controversies regarding genetically modified (GM) foods. This
experience can be used to generate class interest and to highlight the importance of good
information when making judgments. Consider starting class with a headline addressing one
of these issues.
Teaching Tips
1. Annual flu vaccinations are a common example of using vaccines to prevent diseases
that cannot be easily cured. However, students might not understand why many people
receive the vaccine every year. A new annual vaccine is necessary because the flu viruses
keep evolving.
2.Genetically engineered organisms are controversial, creating various degrees and
directions of social resistance; yet many debates around issues of science are confused by
misinformation. This may be an opportunity for you to make an extra credit or regular
assignment for students to take a position, on one side or the other, on some aspect of this or
related issues. The science would need to be accurate. Students might debate whether a food
product made from GM/transgenic organisms should be labeled as such, or students can
discuss the risks or advantages of producing GM organisms.
3.The origin of the name “restriction enzymes” may be of interest. In nature, these enzymes
protect bacterial cells against foreign DNA. Thus, these enzymes “restrict” the invasion of
foreign genetic material.
4.The ability to swap genes between prokaryotes and eukaryotes using the technologies
described in this chapter reveal the fundamental genetic mechanisms shared by all forms of
life. This very strong evidence of common descent is a lesson about evolution that may be
missed by your students.
5.Students might think you are just making a bad joke by noting that laboratory-synthesized
genes are “designer genes,” but this is a common term. Search the Internet using the
keywords “designer genes,” and many scientific (and unscientific) sites will be found.
6.A genomic library of the sentence you are now reading would be all of the sentence
fragments that make up the sentence. One could string together all of the words of this first
sentence, without spaces between letters, and then conduct a word-processing edit placing a
space between any place where an “e” is followed by the letter “n.” The resulting fragments
of this original sentence would look like this, and would be like a type of “genomic library.”
Age nomic library of these nte nce you are now reading would be all of these nte nce
fragments that made up these nte nce.
7.Some Internet search programs rely on a methodology similar in one way to the use of a
nucleic acid probe. For example, if you want to find the lyrics to a particular song, but you
do not know the song title or artist, you might search the Internet using a unique phrase
from the song. (For example, search using “yellow submarine.”) The search engine will
scan millions of web pages to identify those sites containing that particular phrase.
However, unlike a nucleic acid probe, you would search for the song by using a few of the
lyrics. A nucleic acid probe would search using a sequence complementary to the desired
sequence.
8.Roundup Ready Corn, a product of Monsanto, is resistant to the herbicide Roundup. The
general strategy for farmers is to spray fields of Roundup Ready corn with the herbicide
Roundup, killing weeds but not the corn. A search of the Internet will quickly reveal the
controversy associated with this and other genetically modified organisms (GMO), which
can encourage interesting discussions and promote critical thinking skills.
9.As gene therapy technology expands, our ability to modify the genome in human
embryos, created through in vitro fertilization, permits genetic modification at the earliest
stages of life. Future generations of humans, like our crops today, may include those with
and without a genetically modified ancestry. The benefits and challenges of these
technologies raise issues many students have never considered. Our students, and the
generations soon to follow, will face the potential of directed human evolution.
DNA Profiling and Forensic Science
Student Misconceptions and Concerns
1. Television programs might lead some students to expect that DNA profiling is quick
and easy. Ask students to consider why DNA profiling actually takes many days or weeks to
complete.
2.The many forms of DNA technology discussed in this chapter provide powerful evidence
of evolution. Although not addressed regularly in this chapter, consider reminding students
that these techniques continue to reinforce and inform our understandings of the common
decent of life on Earth.
Teaching Tips
1. In most legal cases, the probability of two people having identical DNA profiles ranges
from one in 100,000 to one in 1 billion or more; yet eyewitness testimony has been a
standard part of the justice system. If you want to make the point about the unreliability of
eyewitnesses in a trial, compared to techniques such as genetic profiling, consider this
exercise. Arrange for a person who is not well known to the class to run into your
classroom, take something you have placed near you (perhaps a bag, stack of papers, box),
and leave quickly. You need to take care that no one in the class is so alarmed as to do
something dangerous. Once the “thief” is gone, tell the class that this was planned but not to
speak. Have them each write a description of the person, including height, hair color,
clothing, facial hair, behavior, and so on. Many students will be accurate, but some will
likely get details wrong. This is also an effective exercise to demonstrate the need for large
sample sizes and accurate recording devices for good scientific technique.
2.In PCR, the product becomes another master copy. Imagine that while you are
photocopying, every copy is used as a master at another copy machine. (This would require
many copy machines.)
3.Students might need a little more practice understanding the products of restriction
enzymes. Consider these two words, equilibrium and equalibrium. Imagine that a mutation
produced the spelling error of the second word. If we used a “restriction enzyme” that splits
these words between “u” and “i,” how will the fragments compare in size and number?
equilibrium = equ ilibri um (3 fragments of 3, 6, and 2 letters)
equalibrium = equalibri um (2 fragments of 9 and 2 letters)
4.Separating marker ink using paper chromatography is a simple experiment that
approximates some of what occurs in gel electrophoresis. Consider doing this as a class
demonstration while addressing electrophoresis. Cut a large piece of filter paper into a
rectangle or square. Use markers to color large dots about 2 cm away from the edge of the
paper. Separate the dots from each other by 3–4 cm. Place the paper on edge, dots down,
into a beaker containing about 1 cm of ethanol or isopropyl alcohol (50% or higher will do).
The dots should not be in contact with the pool of alcohol in the bottom of the beaker. As
the alcohol is drawn up the filter paper by capillary action, the alcohol will dissolve the ink
dots. As the alcohol continues up the paper, the ink follows. Not all of the ink components
move at the same speed, based on their size and chemical properties. If you begin the
process at the start of class, you should have some degree of separation by the end of a 50minute period. Experiment with the technique a day or two before class to fine-tune the
demonstration, and experiment with different types of ink. (Save and air-dry these samples
for your class.) Consider using brown, green, and black markers because these colors are
often made by color combinations.
Genomics and Proteomics
Student Misconceptions and Concerns
1. The text notes that there are 24 chromosomes in the human genome. Students might
initially find this confusing, as it is common knowledge that humans have 23 pairs of
chromosomes. Consider making the statement that we have 24 different types of
chromosomes and asking your students to explain why this is true.
2.The similarities of the genotypes and phenotypes of members of a human family tree are
expected and understood by most students. Yet, for many students, these same relationships
are often poorly extrapolated to phylogenetic relationships of other groups. The use of
genomics to test phylogenetic relationships is an enormously powerful tool used in modern
systematics. Genomics is a significant test of the other overwhelming types of evidence for
evolution.
Teaching Tips
1. The first targets of genomics were prokaryotic pathogenic organisms. Consider asking
your students in class to suggest the reasons why this was a good choice. Students will
likely note that the genomes of these organisms are smaller than those of eukaryotes and
that many of these organisms are of great medical significance.
2.The authors note that there are 3.2 billion nucleotide pairs in the human genome. There
are about 3.2 billion seconds in 101.4 years. This simple reference might add meaning to the
significance of these large numbers.
3.The main U.S. Department of Energy Office website in support of the Human Genome
Project is found at www.ornl.gov/sci/techresources/Human_Genome/ home.shtml.
4.The website for the National Center for Biotechnology Information is
(www.ncbi.nlm.nih.gov/). The center, established in 1988, serves as a national resource for
biomedical information related to genomic data.
5.Challenge students to explain why a complete understanding of an organism’s genome
and the resulting proteins produced is still not enough to understand the full biology of an
organism. Challenge them to consider the role of the environment in development and
physiology. (One striking example of the influence of the environment is that the sex of
some reptiles is determined not by genetics, but by incubation temperature!)
6.With a better understanding of the diverse and still unknown roles of many sections of
DNA, consider discussing some of the difficulties of “resurrecting” extinct organisms from
incomplete DNA sequences.
Human Gene Therapy
Student Misconceptions and Concerns
1.Using gene therapy to “fix” genetic problems relies on a thorough understanding of the
roles of genes and alleles. Students might benefit from a discussion of the extent to which
we as a society might want to consider directing our own genetics.
Teaching Tips
1. Ethical, legal, and social issues related to the Human Genome Project are directly
addressed at the Department of Energy Human Genome website at
www.ornl.gov/sci/techresources/Human_Genome/elsi/elsi.shtml.
2.The Biology and Society end-of-chapter textbook questions address some of the issues
raised in this chapter section.
Safety and Ethical Issues
Student Misconceptions and Concerns
1.The many issues raised in this chapter are of great potential significance and remain
unresolved. An informed debate about rights, responsibilities, and possibilities is currently
engaged in modern society regarding these scientific issues.
The Genetic Information Nondiscrimination Act was passed in May 2008. Details about this
important legislation can be found at
www.ornl.gov/sci/techresources/Human_Genome/elsi/legislat.shtml.
Teaching Tips
1. Genetically engineered organisms are controversial, creating various degrees of
concern; yet many debates around issues of science are confused by misinformation. This
may be an opportunity for you to make an extra credit or regular assignment for students to
take a position, on one side or the other, on some aspect of genetic engineering. The science
would need to be accurate. Students might debate whether a food product made from
GM/transgenic organisms should be labeled as such, or students can discuss the risks or
advantages of producing GM organisms.
2.A person was recently heard to declare their opposition to GM food by stating “I do not
want any DNA in my food.” You might want to have your students respond to this person’s
concerns.
Answers to End-of-Chapter Questions
The Process of Science
11. Suggested answer: The biochemist could start with DNA isolated from liver cells (the
entire genome) and carry out the procedure outlined in Figure 12.8 to produce a collection
of recombinant bacterial clones, each carrying a small piece of liver cell DNA. To find the
clone with the desired gene, the biochemist could then make a probe of radioactive RNA
with a nucleotide sequence complementary to part of the gene: GACCUGACUGU. This
probe would bind to the gene, labeling it, and identifying the clone that carries it.
Alternatively, the biochemist could start with messenger RNA (mRNA) isolated from liver
cells and use it as a template to make DNA (using reverse transcriptase). Cloning this DNA
rather than the entire genome would yield a smaller library of genes to be screened—only
those active in liver cells. Furthermore, the genes would lack introns, making the desired
gene easier to manipulate after isolation.
12. Suggested answer: Determining the nucleotide sequences is just the first step. Once
researchers have written out the DNA “book,” they will have to try to figure out what it
means—what the nucleotide sequences code for and how they work. In addition, researchers
will attempt to use this information to help identify alleles that cause specific disease and
ultimately hope to be able to use this information to cure genetic diseases.
Biology and Society
13. Some issues and questions to consider: What kinds of impact will gene therapy have on
the individuals who are treated? On society? Who will decide what patients and diseases
will be treated? What costs will be involved, and who will pay them? How do we draw the
line between treating disorders and “improving” the human species?
14. Some issues and questions to consider: What are some of the unknowns in recombinant
DNA experiments? Do we know enough to anticipate and deal with possible unforeseen and
negative consequences? Do we want this kind of power over evolution? Who should make
these decisions? If scientists doing the research were to make the decisions about guidelines,
what factors might shape their judgment? What might shape the judgment of business
executives in the decision-making process? Does the public have a right to a voice in the
direction of scientific research? Does the public know enough about biology to get involved
in this decision-making process? Who represents “the public”?
15. Some issues and questions to consider: Who made the decision about the safety of the
corn? Was it an individual or more than one person? Did these scientists analyze the safety
data available? Is using the corn a better option than allowing people to die from starvation?
Did the corn actually contain GM kernels (it is indicated that it was “likely”)? What might
be the associated health risks and could they be as bad as dying from starvation?
16. Some issues and questions to consider: How often are these mistakes made? How many
people are on death row who had a trial that lacked any DNA evidence at the time? Who
should pay for the testing? Would you be willing to pay higher taxes to cover the cost of this
expensive testing? If a person had been convicted in a trial using DNA evidence, should
they get to appeal and have further testing done? The current number of states banning the
death penalty can be found at www.deathpenaltyinfo.org/documents/FactSheet.pdf.
Additional Critical Thinking Questions
The Process of Science
1. PCR is a technology that has many useful applications with biotechnology. What are
some of those applications? What are the advantages of PCR over gene cloning for
generating many copies of a DNA fragment?
Suggested answer: The polymerase chain reaction can be used in a variety of settings
ranging from amplifying DNA from fossils, to forensics, to genetic testing. PCR requires
only a very small amount of DNA as starting material and usually takes only a few hours.
Gene cloning requires larger amounts of DNA for successful transformation of bacterial
cells and requires at least a day for growth of cell cultures.
2.Humans are almost identical in the protein-coding sections of the genome, yet each
individual has a unique DNA profile. Explain how this is possible.
Suggested answer: Large portions of the human genome consist of noncoding DNA. The
highly variable genomic regions analyzed for DNA profiling are located in these noncoding
portions. Humans can still be very similar in their protein-coding regions.
Biology and Society
3. Today, parents at risk of having children with a particular genetic disorder can make use
of preimplantation genetic diagnosis. In this process, a number of embryos are produced by
in vitro fertilization using the parents’ gametes, and a few cells are removed from each
embryo for genetic testing. Those embryos that do not carry the disorder are selected for
implantation, ensuring that children will be free of the disorder. What limits, if any, do you
feel should be put on the use of this procedure?
Some issues and questions to consider: If embryos can be screened for specific genetic
disorders, they can be screened for any specific genetic sequences. It is possible for embryos
to be tested for genetic variations that are not detrimental to health, such as hair color or
intelligence. Parents could select a preferred combination of traits in their potential
offspring. Could this be a “slippery slope” to allowing engineering of traits not carried by
the parents? What is to be done with the healthy embryos that are rejected?
4.The possibility of extensive genetic testing raises questions about how personal genetic
information should be used. For example, should employers or potential employers have
access to such information? Why or why not? Should the information be available to
insurance companies? Why or why not? Is there any reason for the government to keep
genetic files? Is there any obligation to warn relatives who might share a bad gene? Might
some people avoid being tested for fear of being labeled genetic outcasts or for fear that
they will not get or keep health insurance? Or might they be compelled to be tested against
their wishes? Can you think of other reasons to proceed with caution?
Some issues and questions to consider: Should genetic testing be mandatory or voluntary?
Under what circumstances? Why might employers and insurance companies be interested in
genetic data? Since genetic characteristics differ among ethnic groups and between the
sexes, might such information be used to discriminate? Which of these questions do you
think is most important? Which issues are likely to be the most serious in the future?