ABOUT THIS WORKSHEET
This worksheet complements the Click and Learn “CSI Wildlife.” (http://www.hhmi.org/
biointeractive/csi-wildlife).
PROCEDURE
As you proceed through the interactive, follow the instructions and answer the questions in the
space provided.
1. Read the introduction and watch the opening video.
a) What is a keystone species?
When you pull a species out of their ecosystem the whole thing starts to unravel because the
ecosystem is largely dependent on them
b) Dr. Wasser states that approximately 50,000 African elephants are killed each year.
According to the video, it is estimated that there are around 470,000 African elephants. If
these numbers are correct, approximately what percentage of African elephants are killed
each year? (Show your work.)
50,000/470,000= 10.4% each year
c) In one or two sentences, summarize Dr. Wasser’s research and how it is being used to
conserve elephants.
When a shipment of ivory is seized by law enforcement, Dr. Wasser works with them to see where the
ivory was poached from. He applies forensic tools based on DNA analysis to see where it all came from
to see where they can target the law enforcement to.
CASE ONE:
2. Watch the crime scene video on the first slide of Case One. Explain the goal of the case.
Park Rangers found 24 elephants dead with their tusks removed by poachers in Garamba National Park.
Once tissue samples were collected they saw tire trucks leaving the crime scene. They find a truck 600
KM away at the border of Congo and the Central African Republic with a dozen elephant tusks in the
back. The tusks are sent to the lab for analysis.
3. Look at the map provided and list the region or countries the majority of African elephants inhabit.
The Republic of Congo and Gabon is a very large area. Also, the region between Angola, Namibia and
Botswana. South Sudan also has a lot.
Proceed to the How DNA Profiling Works section.
4. What does “STR” stand for?
STR stands for Short Tandem Repeats. All STRs contain a repeat unit of a few bases within a strand of
DNA.
5. Look at the gel on the screen. What do the bands on the gel represent?
The DNA profiling for two different elephants verses the DNA ladder.
, 6. STRs at specific loci have shared characteristics between individuals and/or alleles. Place a check
next to the characteristic(s) that are shared.
Made up of Unit, i.e., CTA
X nucleotides O
Flanking sequence Same number of
X 0 units
7. DNA profiling is also called DNA fingerprinting. A common misconception about DNA fingerprinting is
that the analysis has to do with actual fingerprints. Explain one similarity and one difference
between a human being’s pattern of bands on an electrophoresis gel and a human fingerprint.
Electrophoresis shows a whole DNA sequence while fingerprinting allows you to simply identify a
person. But both share the fact that they are so unique its almost impossible to have 2 people with the
exact sam fingerprint/ DNA sequence.
8. Click on Technique. List three sources to obtain elephant DNA for analysis.
Hair roots, saliva, body tissue
9. Watch the animation on the polymerase chain reaction under Technique. Why are flanking
sequences important for amplifying STR fragments?
It ensures that the regions between the bound primers, which include the repeat units, are amplified.
The end product is a DNA sample that contains billions of copies of individual STR fragments
10. A scientist makes primers specific to a particular STR fragment in elephants. These primers are
then used to amplify the STR fragment from 10 different elephants. Would you expect the fragment
to be the same size in all the elephants? Explain your answer.
No, the fragment would not be the same size in all the elephants. The longest ones will be closest to
the starting point and the shortest ones will be nearest the far end
11. Scientists typically amplify multiple STR fragments from an individual in a single PCR. Explain how
they are able to do that.
Scientists use primers complementary to portions of the flanking sequences at different loci (also
referred to as!markers). This ensures that the regions between the bound primers, which include the
repeat units, are amplified. The end product is a DNA sample that contains billions of copies of
individual STR fragments
12. What is the relationship between the size of a DNA fragment and the distance it migrates in the
gel?
The longer the DNA fragment, the more slowly it moves through the gel.
13. Why does DNA migrate to the positive electrode?
An electrical current is applied to the gel, causing the negatively charged DNA to move toward the
positively charged electrode.!
This worksheet complements the Click and Learn “CSI Wildlife.” (http://www.hhmi.org/
biointeractive/csi-wildlife).
PROCEDURE
As you proceed through the interactive, follow the instructions and answer the questions in the
space provided.
1. Read the introduction and watch the opening video.
a) What is a keystone species?
When you pull a species out of their ecosystem the whole thing starts to unravel because the
ecosystem is largely dependent on them
b) Dr. Wasser states that approximately 50,000 African elephants are killed each year.
According to the video, it is estimated that there are around 470,000 African elephants. If
these numbers are correct, approximately what percentage of African elephants are killed
each year? (Show your work.)
50,000/470,000= 10.4% each year
c) In one or two sentences, summarize Dr. Wasser’s research and how it is being used to
conserve elephants.
When a shipment of ivory is seized by law enforcement, Dr. Wasser works with them to see where the
ivory was poached from. He applies forensic tools based on DNA analysis to see where it all came from
to see where they can target the law enforcement to.
CASE ONE:
2. Watch the crime scene video on the first slide of Case One. Explain the goal of the case.
Park Rangers found 24 elephants dead with their tusks removed by poachers in Garamba National Park.
Once tissue samples were collected they saw tire trucks leaving the crime scene. They find a truck 600
KM away at the border of Congo and the Central African Republic with a dozen elephant tusks in the
back. The tusks are sent to the lab for analysis.
3. Look at the map provided and list the region or countries the majority of African elephants inhabit.
The Republic of Congo and Gabon is a very large area. Also, the region between Angola, Namibia and
Botswana. South Sudan also has a lot.
Proceed to the How DNA Profiling Works section.
4. What does “STR” stand for?
STR stands for Short Tandem Repeats. All STRs contain a repeat unit of a few bases within a strand of
DNA.
5. Look at the gel on the screen. What do the bands on the gel represent?
The DNA profiling for two different elephants verses the DNA ladder.
, 6. STRs at specific loci have shared characteristics between individuals and/or alleles. Place a check
next to the characteristic(s) that are shared.
Made up of Unit, i.e., CTA
X nucleotides O
Flanking sequence Same number of
X 0 units
7. DNA profiling is also called DNA fingerprinting. A common misconception about DNA fingerprinting is
that the analysis has to do with actual fingerprints. Explain one similarity and one difference
between a human being’s pattern of bands on an electrophoresis gel and a human fingerprint.
Electrophoresis shows a whole DNA sequence while fingerprinting allows you to simply identify a
person. But both share the fact that they are so unique its almost impossible to have 2 people with the
exact sam fingerprint/ DNA sequence.
8. Click on Technique. List three sources to obtain elephant DNA for analysis.
Hair roots, saliva, body tissue
9. Watch the animation on the polymerase chain reaction under Technique. Why are flanking
sequences important for amplifying STR fragments?
It ensures that the regions between the bound primers, which include the repeat units, are amplified.
The end product is a DNA sample that contains billions of copies of individual STR fragments
10. A scientist makes primers specific to a particular STR fragment in elephants. These primers are
then used to amplify the STR fragment from 10 different elephants. Would you expect the fragment
to be the same size in all the elephants? Explain your answer.
No, the fragment would not be the same size in all the elephants. The longest ones will be closest to
the starting point and the shortest ones will be nearest the far end
11. Scientists typically amplify multiple STR fragments from an individual in a single PCR. Explain how
they are able to do that.
Scientists use primers complementary to portions of the flanking sequences at different loci (also
referred to as!markers). This ensures that the regions between the bound primers, which include the
repeat units, are amplified. The end product is a DNA sample that contains billions of copies of
individual STR fragments
12. What is the relationship between the size of a DNA fragment and the distance it migrates in the
gel?
The longer the DNA fragment, the more slowly it moves through the gel.
13. Why does DNA migrate to the positive electrode?
An electrical current is applied to the gel, causing the negatively charged DNA to move toward the
positively charged electrode.!
