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Ecology
Revised December 2018
www.BioInteractive.org
Page 1 of 6
Click & Learn
Student Worksheet
CSI Wildlife: Using Genetics to Hunt Elephant Poachers
INTRODUCTION
Forensic scientists collect and analyze scientific evidence to solve crimes. One type of evidence they use is
genetic data. In this activity, you will use DNA analysis to solve several crimes related to elephant conservation,
a field of science known as wildlife forensics. This worksheet complements the Click & Learn CSI Wildlife
.
MATERIALS
• access to the Click & Learn CSI Wildlife
• four-function calculator
PROCEDURE
Congratulations! You have just been hired by an international police force to work as a forensic scientist
dedicated to protecting wildlife and investigating illegal activity where protected animals are involved. In
particular, you will focus on the protection of African elephants. You are excited to put your scientific skills to
work. To help you learn more about what you will do in your new position, your boss asks you to complete
HHMI BioInteractive’s Click & Learn CSI Wildlife. But before you begin, she asks you to answer the following
questions.
1. Elephants are a keystone species and play a pivotal role in shaping the forests and savannas in which they
live. Knowing the importance of elephants, an international group of scientists conducted a census to
estimate the number of African elephants. The Great Elephant Census data were released in August 2016,
and unfortunately, the results reveal that African elephant populations have decreased by 30% in just the
past seven years. Why do you think the number of elephants is declining?
2. You have likely heard of investigators using DNA fingerprinting to identify individuals in crime scene
investigations. Briefly describe your current understanding of the process of DNA fingerprinting.
CSI Wildlife: Using Genetics to Hunt Elephant Poachers
Ecology
Revised December 2018
www.BioInteractive.org
Page 2 of 6
Click & Learn
Student Worksheet 2
Part 1
Now that you have shared with your boss what you already know, she is ready to send you for training.
Complete the activities in Case One of the CSI Wildlife Click & Learn.
3. Your colleagues in the legal department are preparing to take a case to trial. To help them, rewrite your
description of the process of DNA fingerprinting so a jury could understand it.
Now you are ready for your first major assignment. Your colleagues are investigating a newly seized tusk and
wonder if the tusk is from a recently discovered crime where 10 elephants from the same population were
found dead with their tusks removed. The genotype of the seized tusk for five short tandem repeat (STR) loci is
shown in Table 1. Allele names for each of the STR loci correspond to their size in base pairs (bp). Table 2 lists
the genotypes of the same five STR loci for 10 recently slaughtered elephants.
Seized
tusk
FH19
FH60
FH71
FH129
193
193
147
147
103
62
62
152
160
FH19
FH60
FH67
FH71
FH129
Elephant
1
189
193
147
147
97
97
62
64
152
154
Elephant
2
185
193
147
147
95
103
62
62
152
152
Elephant
3
183
185
147
147
95
97
62
64
152
162
Elephant
4
193
193
147
147
91
105
62
64
152
152
Elephant
5
187
187
145
147
95
95
62
64
152
160
Elephant
6
187
193
145
147
91
97
64
64
152
160
Elephant
7
193
193
149
151
97
97
60
62
156
160
Elephant
8
193
193
147
147
97
103
62
62
152
160
Elephant
9
193
193
147
147
97
97
62
62
160
160
Elephant
10
189
193
147
147
95
105
62
62
152
156
Table 2. Genotypes using five STR loci for 10 slaughtered elephants.
Table 1. Genotype for five STR loci recovered from a seized elephant tusk.
CSI Wildlife: Using Genetics to Hunt Elephant Poachers
Ecology
Revised December 2018
www.BioInteractive.org
Page 3 of 6
Click & Learn
Student Worksheet 2
4. Did the seized tusk come from one of the recently slaughtered elephants? ________ What evidence
supports your finding?
5. Dr
aw the expected pattern of bands on a gel that shows the alleles for the seized tusk and the elephant you
identified as a potential match for STR loci FH60 and FH129. Include a DNA ladder that has DNA fragments
that are 125, 150, and 175 bp in size.
6. You
r next challenge is to calculate the probability that another elephant from the same population would
have the same genotype as the one from the seized ivory sample.
a. Calculate the frequency of each of the alleles genotyped in the ivory sample using data from the 10
slaughtered elephants. Start by examining the data in Table 2 for STR locus FH19. The ivory sample was
homozygous for the 193-bp allele. In the sample of 10 elephants, 12 alleles out of a total of 20 were also
193 bp in size. Look at how these data are used to determine the frequency of the allele in Table 3. Use
the same approach to calculate the frequency of the alleles for the other four STR loci and record your
answers in the table. Some of the data is provided for you.
Table 3. Frequency of alleles for five different STR loci in the group of slaughtered elephants.
STR locus
FH19
FH60
FH67
FH71
FH129
# of copies of Allele 1 in the group
of 10 elephants studied
12 16 9
Total number of alleles in the
group of 10 elephants studied
20 20
Frequency of Allele 1
12/20
= 0.60
Number of copies of Allele 2 in
the group of 10 elephants studied
12 2
Total number of alleles in the
group of 10 elephants studied
20 20
Frequency of Allele 2
12/20
= 0.60
CSI Wildlife: Using Genetics to Hunt Elephant Poachers
Ecology
Revised December 2018
www.BioInteractive.org
Page 4 of 6
Click & Learn
Student Worksheet 2
b. Use the formulas below to calculate the probability of another individual having the same genotype for
each individual locus. Enter the formulas and probability in Table 4.
• If the ivory sample is homozygous for an STR locus, the probability (P
(genotype for locus X)
) that another
individual has the same genotype for the STR locus is:
P
(genotype for locus X)
= (frequency of Allele 1)
2
• If the ivory sample is heterozygous for an STR locus, the probability (P
(genotype for locus X)
) that another
individual has the same genotype for the STR locus is:
P
(genotype for locus X)
= 2 × (frequency of Allele 1) × (frequency of Allele 2)
STR locus
FH19
FH60
FH67
FH71
FH129
Formula with filled-in
values for the probability
(0.60)
2
Calculated probability for
the locus
0.36
Table 4. The probability that another elephant in the same population has the same genotype at each individual STR locus,
based on the allele frequencies in Table 3.
c. To determine the probability that another individual has the same genotype for each of the five STR loci
(in other words, the same genetic fingerprint), multiply all the individual probabilities together. What is
the probability that all five match? __________
7. Impressed with your work, your boss now asks you to apply what you have learned to the genotype for the
ivory sample for all 16 STR loci, listed in Table 5 below. The first five STR loci are the same as the ones listed
in Table 4. In addition, your colleague has been able to collect additional samples of elephants from the
same population as the ones shown in Table 2. He now has allele frequency data based on 80 alleles, shown
in the table below.
STR locus
FH19
FH60
FH67
FH71
FH129
FH39
FH40
FH48
Allele 1 size (bp)
193
147
97
62
152
239
242
170
Allele 1 frequency
0.28
0.66
0.36
0.51
0.39
0.31
0.68
0.05
Allele 2 size (bp)
193
147
103
62
160
243
242
172
Allele 2 frequency
0.28
0.66
0.10
0.51
0.25
0.41
0.68
0.38
STR locus
FH94
FH102
FH103
FH126
FH127
FH153
S03
S04
Allele 1 size (bp)
225
177
149
94
247
169
141
154
Allele 1 frequency
0.65
0.64
0.13
0.18
0.04
0.011
0.55
0.8
Allele 2 size (bp)
225
181
151
110
247
171
143
154
Allele 2 frequency
0.65
0.14
0.61
0.11
0.04
0.08
0.39
0.8
Table 5. Allele size and frequency for 16 STR loci from a sample of 40 elephants (80 alleles).
a. Compare the frequency of the alleles for STR loci FH19, FH60, FH67, FH71, and FH129 that you
completed in Table 3 with the values in Table 5. Why do you think the values differ?
b. Calculate the probability that another individual has the same genotype at all 16 STR loci by using the
same procedure as Questions 6b and 6c. What is the probability of an identical match with another
elephant at all 16 STRs? __________________
CSI Wildlife: Using Genetics to Hunt Elephant Poachers
Ecology
Revised December 2018
www.BioInteractive.org
Page 5 of 6
Click & Learn
Student Worksheet 2
Part 2
Your colleagues can tell that you have the necessary skills to help stop the killing of elephants for ivory and to
bring poachers to justice. Your boss promotes you to lead a new case. To solve this case, you first need to
complete Case Two of the CSI Wildlife Click & Learn.
The details of the case: Another shipment of ivory has been seized. Law-enforcement officials captured one of
the people shipping the ivory. Through interviews with this individual and his contacts, the police determine the
timing of the poaching event, but they still do not know
the location. At the time the ivory was collected, three
suspects were each caught poaching elephants in parks in
three different parts of Africa. Suspect 1 was poaching in
Tanzania, Suspect 2 in Cameroon, and Suspect 3 in
Zambia.
Your boss would like you to link the genotype of one of the seized tusks to a reference population taken from
one of the three countries. You determine the genotype of the seized tusk for four STR loci, shown in Table 6.
Your lab assistant summarizes the allele frequency data for the three possible source populations in Figure 1
below.
FH39
FH67
FH103
FH129
239
97
151
154
241
97
153
160
STR Loci
FH39
FH67
Allele frequencies
from three
elephant
populations
Alleles in seized tusk
239, 241
97, 97
STR Loci
FH103
FH129
Allele frequencies
from three
elephant
populations
Alleles in seized tusk
151, 153
154, 160
Table 6. The genotype for four STR loci of a seized tusk.
Figure 1. Comparison of the alleles from the ivory tusk to those of the reference populations in Tanzania, Zambia, and Cameroon.
CSI Wildlife: Using Genetics to Hunt Elephant Poachers
Ecology
Revised December 2018
www.BioInteractive.org
Page 6 of 6
Click & Learn
Student Worksheet 2
8. Make a claim about which country in Africa is most likely to be near the source population of the seized
tusks. Your claim will be used in court, so make sure to highlight the evidence you used to make your claim.
Part 3
Late one night, rangers in a park hear a gunshot and quickly move to investigate. One
elephant has been slain, but the quick actions of the rangers make the poacher flee,
which saves the lives of many elephants. Eventually, a suspect is captured with one
pair of elephant tusks. Your boss gives you the tusk and a blood sample from the killed
elephant. She asks you to determine whether the tusks came from the elephant that
was killed. You analyze the samples and the results are shown in Figure 1. Each STR
locus is shown in a different color.
9. Use the evidence in Figure 2 to determine whether the tusk came from the slain
elephant. Write a brief summary of your findings for the case file.
10. It is very important for scientists to consider sources of error in an experiment and alternative explanations.
What sources of error or alternative explanations might change the answer you gave in Question 9?
11. Af
ter completing this activity, do you believe that DNA fingerprinting is useful as evidence in criminal cases
and can help in reducing elephant poaching? Provide three pieces of evidence from this experience to
support your answer.
Figure 2. The gel with the alleles for
four different STR loci for the
elephant tusk and the killed elephant.
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