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 meth...
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.
, - 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.
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