Gizmos : DNA Profiling
Vocabulary: DNA polymerase, DNA profiling, gel electrophoresis, gene, mutation, non-coding
region, polymerase chain reaction, primer, short tandem repeat
Gizmo Warm-up
DNA profiling does not ju
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Gizmos : DNA Profiling
Vocabulary: DNA polymerase, DNA profiling, gel electrophoresis, gene, mutation, non-coding
region, polymerase chain reaction, primer, short tandem repeat
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
DNA contains genes and non-coding regions
section. You are looking at a strand of DNA.
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.
These sections are different for those three people. One is shorter, while another is
longer. Therefore, these sections are not the same.
2. Click Previous then click on Gene A. Are there differences in gene A for the three people?
There is no different in gene A for the three people. They are all equal in length.
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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?
The sequence TAAA is repeated in the middle of each of the 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?
This makes the legend shorter or longer. If it has less STR, the length will be shorter as if it
has more STR, the length will be longer.
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?
They attach on each other. AAGGC attaches onto TCGCC while TCGCC attaches onto
AAGGC for all 3 people.
4. Observe: Click Next. An enzyme called DNA polymerase uses the primers as a starting
point to copy the DNA. Copying DNA using primers is a technique called Polymerase
chain reaction (PCR).
Click Next again. The DNA segments are copied millions of times.
What do you notice about the lengths of the copied DNA strands?
The lengths of the copied DNA Strands are different for each
person.
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