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Exploring DNA Profiling

Learn how DNA profiling helps identify individuals through unique genetic patterns. This student activity explores real-world applications like forensics and genealogy using simulations and key concepts like STRs and gel electrophoresis.

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    Student Exploration: DNA Profiling Directions: Follow the instructions t o g o through the simulation. Respond to the questions and prompts in the orange boxes. 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? 2. What are some possible uses for technology that identify people based on their DNA? The different arrangements/sequences of base pairs help create differences in our DNA can DNA fingerprinting can be used to identify suspects and link them to crime scenes, or the DNA found in our saliva can be used in genealogy and help determine ethnic origins. 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 leam 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 These sections are different as some sections are different in length and have different base pair sequences. Person 1 and 3 have identical sequences in their gene, whereas person 2 has a different nucleotide sequence. 2. Click Previous then click on Gene A. Are there differences in gene A for the three people?

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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? In the middle of each of the three DNA sequences, I see a repeated sequence of TAAA(Top) and A l l i (bottom) 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? A DNA sequence's number of STRs refers to the number of times a certain short sequence of nucleotides is repeated in a given area of the DNA, adding variation in those sections' lengths across people. 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? I noticed that the primers attach to the same parts of the DNA strand; the beginning and ends. 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)

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    Click Next again. The DNA segments are copied millions of times. What do you notice about lhe lengths of the copied DNA sirands? I noticed that the lengths of lhe copied DNA strands are different for each individual 5. Compare: Click Next Gel electrophoresis is used Io separate DNA strands of different lengths. An electric current is passed through the gel. As the current moves from top to bottom, il pulls lhe DNA and loading dye along wilh it. Click on the power box Io turn il on. A. Which person's DNA band traveled the farthest? Person 2 Shortesl? Person 1 B. Turnon Show labels What do you notice about the length of The longer the strand, the shorter the DNA versus the distance it traveled down lhe gel? it will travel. Additionally, lhe shorter the DNA strand, lhe longer it will travel. C. Can you identify people by comparing the length of STR regions on a gel? Explain Yes. you're able to identify people by comparing the length of STR regions on a gel as lhe length of STR regions differ from person to person. Because of this separation, lhe gel acquires a distinctive pattern of bands that corresponds to the sizes of the various STR fragments in lhe sample. If a sample matches any of the known people, it may be determined by comparing the pattern of bands on the gel from the sample to those patterns. 6. Observe: Click Next. Then select Gene A. A. Does gene A have any STRs? Gene A does not have any STRs Because genes are segments of DNA that hold lhe instructions for producing proteins they usually don't have large variable regions like STRs. B. Are there any differences in gene A between the individuals? Person 1 and 3 have identical sequences, whereas person 2 has different ones. Genes may contain small mutations that don't affect the length of the segment. Create primers and copy the DNA. What do you notice about the length of the duplicated regions? They re all the same length.

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