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Student Exploration: DNA Profiling
Vocabulary: DNA polymerase, DNA profiling, gel electrophoresis, gene, mutation, non-coding region,
polymerase chain reaction, primer, short tandem repeat
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
In 1985, Darryl Hunt was convicted of murder. While Hunt was in jail, a new method for analyzing
DNA evidence was invented. The DNA evidence on the victim did not match Hunt’s DNA but did
match that of another prisoner. After 19 years spent behind bars, Hunt was finally declared innocent and
released from prison in 2004.
1. DNA is used to tell people apart. What aspects of DNA do you think make this
possible?
The lengths of the repeated sequences in DNA
The DNA sequences themselves
2. What are some possible uses for technology that can identify people based on their DNA?
Gel electrophoresis
Gizmo Warm-up
DNA profiling does not just compare people’s entire genome side by
side. Instead, a very particular part of the DNA is compared. In the DNA
Profiling Gizmo you will learn about the differences in DNA that make
DNA profiling possible and you will use that knowledge to design your
own DNA profiling test.
Click on the crime lab in the Forensic training section. You are looking at a strand of DNA. DNA contains
genes and non-coding regions between genes. Click on Non-coding A.
1. You are looking at a portion of the non-coding A section for three different people. Are these
sections the same or different? Explain.
- The sections are different. Person 1 has the longest section, person 3 has the second-
longest section and person 2 has the shortest section.
a. Click Previous then click on Gene A. Are there differences in gene A for the three
people?
, - Person 1 and Person 3 have identical sequences in their gene A. On the other hand, the sequence
of nucleotides in person 2 differs from both persons 1 and 3. In one section, persons 1 and 3 have
the base pair of C and G whereas person 2 has the base pair of A and T.
Activity A: Get the Gizmo ready:
Forensic training ● Click on Forensic training and Start again.
Introduction: In this activity, you will learn about the principles and techniques that make DNA
profiling possible. Genes code for specific traits. In people, the DNA sequences for most genes are
nearly identical, since any change could result in a harmful disorder. The areas between genes do not
code for any essential traits, so a change to the DNA sequence doesn’t have any major consequences. As
a result, these regions tend to be very different for different people.
Question: How can the differences in DNA be exploited to perform DNA profiling?
1. Observe: Click on non-coding A. What do you see in the middle of each of the three DNA
sequences?
- I see repeated sequences (TAAA and ATTT) in all three DNA sequences.
2. Compare: Turn on Show short tandem repeats (STRs). An STR is a short, repeated sequence of
DNA, like TAAA. They can be repeated any number of times without affecting the traits of the
person. Different people usually have different numbers of repeats.
What does this do to the length of each person’s non-coding regions?
- The more STRs a person has in their DNA, the longer their non-coding regions. Vice
versa, the fewer STRs a person has, the shorter their non-coding regions.
3. Create: Your goal is to make copies of the STR region. To do this, you will make primers that
surround the STR region. A primer is a short sequence of DNA that acts as a starting point for
DNA replication.
Click Next. Click on person 1’s DNA to separate the two strands. Drag along the AAGGC
nucleotides, and then the TCGCC nucleotides to create primers. Click Next. The Gizmo will add the
same primers to the two other people.
What do you notice about where the primers attach in each person?
- In all 3 people, the primers attach to the same parts of the DNA strand. One primer attaches to
the beginning of the top strand and the other primer attaches to the end of the bottom strand
for all 3 individuals.
Student Exploration: DNA Profiling
Vocabulary: DNA polymerase, DNA profiling, gel electrophoresis, gene, mutation, non-coding region,
polymerase chain reaction, primer, short tandem repeat
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
In 1985, Darryl Hunt was convicted of murder. While Hunt was in jail, a new method for analyzing
DNA evidence was invented. The DNA evidence on the victim did not match Hunt’s DNA but did
match that of another prisoner. After 19 years spent behind bars, Hunt was finally declared innocent and
released from prison in 2004.
1. DNA is used to tell people apart. What aspects of DNA do you think make this
possible?
The lengths of the repeated sequences in DNA
The DNA sequences themselves
2. What are some possible uses for technology that can identify people based on their DNA?
Gel electrophoresis
Gizmo Warm-up
DNA profiling does not just compare people’s entire genome side by
side. Instead, a very particular part of the DNA is compared. In the DNA
Profiling Gizmo you will learn about the differences in DNA that make
DNA profiling possible and you will use that knowledge to design your
own DNA profiling test.
Click on the crime lab in the Forensic training section. You are looking at a strand of DNA. DNA contains
genes and non-coding regions between genes. Click on Non-coding A.
1. You are looking at a portion of the non-coding A section for three different people. Are these
sections the same or different? Explain.
- The sections are different. Person 1 has the longest section, person 3 has the second-
longest section and person 2 has the shortest section.
a. Click Previous then click on Gene A. Are there differences in gene A for the three
people?
, - Person 1 and Person 3 have identical sequences in their gene A. On the other hand, the sequence
of nucleotides in person 2 differs from both persons 1 and 3. In one section, persons 1 and 3 have
the base pair of C and G whereas person 2 has the base pair of A and T.
Activity A: Get the Gizmo ready:
Forensic training ● Click on Forensic training and Start again.
Introduction: In this activity, you will learn about the principles and techniques that make DNA
profiling possible. Genes code for specific traits. In people, the DNA sequences for most genes are
nearly identical, since any change could result in a harmful disorder. The areas between genes do not
code for any essential traits, so a change to the DNA sequence doesn’t have any major consequences. As
a result, these regions tend to be very different for different people.
Question: How can the differences in DNA be exploited to perform DNA profiling?
1. Observe: Click on non-coding A. What do you see in the middle of each of the three DNA
sequences?
- I see repeated sequences (TAAA and ATTT) in all three DNA sequences.
2. Compare: Turn on Show short tandem repeats (STRs). An STR is a short, repeated sequence of
DNA, like TAAA. They can be repeated any number of times without affecting the traits of the
person. Different people usually have different numbers of repeats.
What does this do to the length of each person’s non-coding regions?
- The more STRs a person has in their DNA, the longer their non-coding regions. Vice
versa, the fewer STRs a person has, the shorter their non-coding regions.
3. Create: Your goal is to make copies of the STR region. To do this, you will make primers that
surround the STR region. A primer is a short sequence of DNA that acts as a starting point for
DNA replication.
Click Next. Click on person 1’s DNA to separate the two strands. Drag along the AAGGC
nucleotides, and then the TCGCC nucleotides to create primers. Click Next. The Gizmo will add the
same primers to the two other people.
What do you notice about where the primers attach in each person?
- In all 3 people, the primers attach to the same parts of the DNA strand. One primer attaches to
the beginning of the top strand and the other primer attaches to the end of the bottom strand
for all 3 individuals.
