Directions: The following story is about a crime solved through biotechnological techniques. The techniques used are DNA fingerprinting and polymerase chain reaction (PCR). DNA fingerprinting is a technique in which an individual’s DNA is analyzed to reveal the pattern of particular short nucleotide sequences. This pattern is claimed to be unique to the individual concerned and can thus be used for identification purposes. Polymerase chain reaction, on the other hand, is a technique used to replicate a DNA fragment so as to produce many copies of a particular DNA sequence. Why do you think there’s a need to generate several copies of the DNA? You will learn the answers to this as you go through the story. Read the story carefully and answer the questions that follow. Questions:1. How did the investigators conclude that the suspect was indeed the murderer? 2. What if a strand of hair was found in the truck bed instead of a seed pod, do you think it will still lead to the identification of the suspect?3. What do you think are the other uses of DNA fingerprinting?4. Why do you think the discovery of the seed pods provided the most crucial clue?5. What were the clues that led to the identification of the suspect?6. What if the strand of hair belonged to the victim, what other clues would you look for? Helentjaris was then given the two seed pods from the suspect's truck along withpods collected by investigators from 12 palo verde trees present in the general vicinityof the factory. The investigators knew which of the 12 trees was the key one at thecrime scene, but did not tell Helentjaris. He extracted DNA from seeds taken fromcach and performed PCR on cach sample. The results of this “blind" cxpcriment wereunmistakable. The pattern from one of the pods found in the truck exactly matched thepatterns from only one of the 12 trees, the one nearest the body.Helentjaris' analysis was admitted as evidence in the trial, the first time the DNAfingerprint of a plant had been used in a court case. This information was critical inplacing the suspect at the crime scene. At the completion of the five-week trial, thesuspect was found guilty of first-degree murder. His conviction was upheld uponappeal, and he is currently serving a life sentence without parole. The Case of the Telltale Palo VerdeOn the night of May 2, 1992, a woman from Phoenix, Arizona, U.S.A. wasstrangled and her body was dumped near an abandoned factory in the surroundingdesert. Police discovered a pager near the body, making its owner the prime suspect inthe murder. When questioned, the man admitted being with the woman on the day ofthe murder, but claimed he had never been near the factory. He suggested that thewoman must have stolen his pager from his pickup truck. A scarch of the pickup truckprovided the crucial clue. It placed the suspect in the factory. On the track hed weretwo seeds from a palo verde tree.The palo verde tree is an unusual plant native to the desert of the Southwest. Amember of the bean family, it develops into a small shrubby trec. Well-adapted to thehot, dry climate, it has very small leaves. To compensate for this, its stems becomegreen and carry out food production. This adaptation gives the plant its name-paloverde, which is Spanish for "green stem." The plant may not resemble beans in somerespects, but like a typical bean, it produces seeds in pods that mature and drop to theground.The homicide investigators assigned to the case asked themselves the followingquestion: Could it be proven that the seed pods found in the bed of the suspect's truckhad fallen from one of the palo verde trees close to where the body was found? If so,it would be a key picce of evidence, placing the suspect at the crime seene anddestroying his alibi. But how could this be demonstrated? The investigators turned toDr. Timothy Helentjaris, then at the University of Arizona, in nearby Tucson.Helentjaris proceeded to determine whether the DNA fingerprint of the seed podsfrom the pickup truck matched that of one of the palo verde trees at the crime scene.Helentjaris knew that to make the match between a seed pod and a tree significant, hewould first have to demonstrate that palo verdes show genetic variation from one treeto another. Otherwise, it would be impossible to clearly link a given pod to oneparticular tree. Fortunately, he found considerable differences in DNA fingerprintsbetween individual plants.Helentjaris was then given the two seed pods from the suspect's truck along withpods collected by investigators from 12 palo verde trees present in the general vicinityof the factory. The investigators knew which of the 12 trees was the key one at thecrime scene, but did not tell Helentjaris. He extracted DNA from seeds taken fromcach and performed PCR on cach sample. The results of this "blind" experiment wereunmistakable. The pattem from one of the pods found in the truck exactly matched thepatterns from only one of the 12 trees, the one nearest the body.

Answered: . How did the investigators conclude…

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Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

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Directions: The following story is about a crime solved through biotechnological techniques. The techniques used are DNA fingerprinting and polymerase chain reaction (PCR). DNA fingerprinting is a technique in which an individual’s DNA is analyzed to reveal the pattern of particular short nucleotide sequences. This pattern is claimed to be unique to the individual concerned and can thus be used for identification purposes. Polymerase chain reaction, on the other hand, is a technique used to replicate a DNA fragment so as to produce many copies of a particular DNA sequence. Why do you think there’s a need to generate several copies of the DNA? You will learn the answers to this as you go through the story. Read the story carefully and answer the questions that follow.

Questions:

1. How did the investigators conclude that the suspect was indeed the murderer?

2. What if a strand of hair was found in the truck bed instead of a seed pod, do you think it will still lead to the identification of the suspect?

3. What do you think are the other uses of DNA fingerprinting?

4. Why do you think the discovery of the seed pods provided the most crucial clue?

5. What were the clues that led to the identification of the suspect?

6. What if the strand of hair belonged to the victim, what other clues would you look for?

Helentjaris was then given the two seed pods from the suspect's truck along with
pods collected by investigators from 12 palo verde trees present in the general vicinity
of the factory. The investigators knew which of the 12 trees was the key one at the
crime scene, but did not tell Helentjaris. He extracted DNA from seeds taken from
cach and performed PCR on cach sample. The results of this “blind" cxpcriment were
unmistakable. The pattern from one of the pods found in the truck exactly matched the
patterns from only one of the 12 trees, the one nearest the body.
Helentjaris' analysis was admitted as evidence in the trial, the first time the DNA
fingerprint of a plant had been used in a court case. This information was critical in
placing the suspect at the crime scene. At the completion of the five-week trial, the
suspect was found guilty of first-degree murder. His conviction was upheld upon
appeal, and he is currently serving a life sentence without parole.

The Case of the Telltale Palo Verde
On the night of May 2, 1992, a woman from Phoenix, Arizona, U.S.A. was
strangled and her body was dumped near an abandoned factory in the surrounding
desert. Police discovered a pager near the body, making its owner the prime suspect in
the murder. When questioned, the man admitted being with the woman on the day of
the murder, but claimed he had never been near the factory. He suggested that the
woman must have stolen his pager from his pickup truck. A scarch of the pickup truck
provided the crucial clue. It placed the suspect in the factory. On the track hed were
two seeds from a palo verde tree.
The palo verde tree is an unusual plant native to the desert of the Southwest. A
member of the bean family, it develops into a small shrubby trec. Well-adapted to the
hot, dry climate, it has very small leaves. To compensate for this, its stems become
green and carry out food production. This adaptation gives the plant its name-palo
verde, which is Spanish for "green stem." The plant may not resemble beans in some
respects, but like a typical bean, it produces seeds in pods that mature and drop to the
ground.
The homicide investigators assigned to the case asked themselves the following
question: Could it be proven that the seed pods found in the bed of the suspect's truck
had fallen from one of the palo verde trees close to where the body was found? If so,
it would be a key picce of evidence, placing the suspect at the crime seene and
destroying his alibi. But how could this be demonstrated? The investigators turned to
Dr. Timothy Helentjaris, then at the University of Arizona, in nearby Tucson.
Helentjaris proceeded to determine whether the DNA fingerprint of the seed pods
from the pickup truck matched that of one of the palo verde trees at the crime scene.
Helentjaris knew that to make the match between a seed pod and a tree significant, he
would first have to demonstrate that palo verdes show genetic variation from one tree
to another. Otherwise, it would be impossible to clearly link a given pod to one
particular tree. Fortunately, he found considerable differences in DNA fingerprints
between individual plants.
Helentjaris was then given the two seed pods from the suspect's truck along with
pods collected by investigators from 12 palo verde trees present in the general vicinity
of the factory. The investigators knew which of the 12 trees was the key one at the
crime scene, but did not tell Helentjaris. He extracted DNA from seeds taken from
cach and performed PCR on cach sample. The results of this "blind" experiment were
unmistakable. The pattem from one of the pods found in the truck exactly matched the
patterns from only one of the 12 trees, the one nearest the body.

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