Ward's World Activity Guides

MiniPCR Wrongfully Convicted Activity - Student Guide

View, download, and print free resources for your science classroom.

Issue link: https://wardsworld.wardsci.com/i/1525606

Contents of this Issue

Navigation

Page 2 of 25

miniPCR bio™ Electrophoresis Forensics Lab. Wrongfully Convicted? Instructor's and Student's Guide Version: 1.1 - Release February 2022 - © 2022 by miniPCR bio™ Student's Guide P./9 Background and significance Forensic DNA analysis - DNA analysis is considered the gold standard in forensic science. But why is this the case? When comparing two people's DNA, more than 99% will be identical. Even with so much similarity, there are more than enough differences to make every person's genetic sequence unique. This makes DNA analysis a powerful tool for identification of individuals. Scientists can isolate DNA from biological crime scene evidence, like a bloodstain or a hair follicle, and use the information in the DNA to match the sample to a specific person. As forensic approaches have evolved, there have been several methods for matching DNA evidence to individuals. Most forensic DNA analysis looks at regions of the genome that vary in length between individuals. Short tandem repeats - Most modern forensic DNA analysis focuses on short tandem repeats (STRs). STRs are short sequences, typically 2 to 5 DNA bases, that repeat several times in a row (Figure 1). The number of times the bases repeat, however, varies between people. Therefore, the length of DNA where Figure 1. Short tandem repeats STRs are short DNA sequences that repeat several times in a row. For example, STR 1 is a specific location in the human genome where the sequence GATA is repeated between 5 and 16 times. the STRs are located also varies between people. Forensic scientists take advantage of this and measure these differences in length to compare DNA between individuals. There are many locations in the human genome where the number of copies of a specific STR varies between people. Forensics scientists give each STR a complex name that reflects its location in the genome, but for simplicity, we will refer to an example as STR 1. At this location in the human genome, the sequence GATA is repeated anywhere between 5 and 16 times (Figure 1). STR 1 ...... GATA GATA GATA GATA GATA ...... ...... GATA GATA GATA GATA GATA GATA ...... 5 REPEATS 6 REPEATS ...... GATA GATA GATA GATA GATA GATA GATA ...... 7 REPEATS UP TO 16 REPEATS

Articles in this issue

Archives of this issue

view archives of Ward's World Activity Guides - MiniPCR Wrongfully Convicted Activity - Student Guide