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? Certain aspects of DNA that would make it possible to tell people apart would be found within the specific DNA sequences of a gene. 2. What are some possible uses for technology that can identify people based on their DNA? Some possible uses for technology that can identify people based on their DNA would be fingerprint analysis. In each individual fingerprint, there are DNA sequences that connect people, therefore finding criminals through the use of this tech is possible. 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. They start out the same in the beginning, but right from the start it is obvious that these 3 sections are different lengths. Towards the end of the shortest strand, the bases start changing. 2. Click Previous then click on Gene A. Are there differences in gene A for the three people? There aren't any differences between the 3 people’s genes. Student_Exploration_DNA_Profiling Activity A: Forensic training Get the Gizmo ready: 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 a few short tandem repeats in the middle of each of the 3 DNA sequences for each person. 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 short tandem repeats just make each person’s non-coding region 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 at the beginning and end of each person’s sequence. 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? I notice that they are all different for each person, some shorter than others.