Download DNA fingerprinting webquest (1)

DNA DETECTIVE WORK
Unless you have a twin, no one in the world has a DNA sequence identical to yours.
Although 99 percent of the DNA is the same in all humans, certain segments vary
widely. Differences in these segments are detected through DNA fingerprinting. A small
amount of tissue, such as blood, hair, or semen, is all that is needed to create a DNA
fingerprint. The sample is cut up using enzymes and the segments are separated by
size through gel electrophoresis. DNA is made visible either with radioactive probes or
by staining. This reveals a pattern of bars: the DNA fingerprint. If the two DNA
fingerprints match, they probably came from the same person. If they don't match, they
certainly came from different individuals. In recent years, a number of people convicted
of crimes have been exonerated based on DNA evidence.
Activity
In this exercise, you will learn the basics of DNA fingerprinting and consider the use of
DNA in criminal investigations.
Part 1: The Technique
*Use your browser to go to NOVA’s website about “Killer’s Trail,” the story behind the
man who inspired the Fugitive TV series and later the movie version starring Harrison
Ford:
http://www.pbs.org/wgbh/nova/sheppard/
*Click on the “Chronology of a Murder” section and read about the events that led up to
the murder trial of Dr. Sam Sheppard.
1. In your opinion, what role (if any) did newspaper stories and editorials have in the
outcome of the original trial of Dr. Sam Sheppard?
Part 2: Switched at Birth
Although a rare occurrence, cases of babies switched at birth in a hospital have made
the news in the past. Since an individual’s DNA sequence is unique, with the exception
of identical twins, DNA fingerprinting is a reliable method used to determine the parents
of a given baby. DNA fingerprints can be derived from restriction fragment-length
polymorphism analysis or using the polymerase chain reaction with variable number
tandem repeats. In this activity, you will analyze the results of a DNA fingerprint
conducted on three babies and three sets of parents to determine which baby belongs
to which parent.
Examine the following DNA Fingerprinting Gel:
Compare the bands of each set of parents to each of the babies and determine which
baby belongs to which set of parents. Line up the bands and illustrate which bands each
baby inherited from its mother and from its father.
1. Identify which baby belongs to which set of parents.
2. Explain why not all the bands in the mother’s or father’s profiles have a
counterpart in the baby’s DNA profile.
3. List other examples where DNA fingerprinting could be used to identify an
individual.
4. Where is the largest DNA fragment on the gel? Where is the smallest DNA
fragment on the gel?
Part 3: It’s Not Perfect
Use your browser to go to Frontline's "The Surprisingly Imperfect Science of DNA
Testing" at
https://www.pbs.org/wgbh/frontline/article/the-surprisingly-imperfect-science-of-dna-testi
ng-2/.
Also view the embedded video (https://www.youtube.com/watch?v=fXsn5VoKokg)
1. According to the article and video, what are the major reasons to NOT trust DNA
evidence?
2. What new problems are being created by modern advanced DNA identification
technology?
Additional info about DNA Fingerprinting:
http://www.dnai.org/d/index.html?m=1
http://labcenter.dnalc.org/labs/dnafingerprintalu/dnafingerprintalu_d.html