You may have heard the name "CODIS" mentioned in nearly any American crime drama on television or in the news. Its name stands for Combined DNA Index System, and the system contains about 10 million profiles of convicted offenders, unsolved crime scene evidence, and missing persons. It relies on a set of 13 genetic markers, known as the "core loci," which are then used to solve cases. It is the largest system of its kind in the world and has assisted more than 141,000 investigations.
Earlier this year, however, the FBI formed a six-person group to review the DNA profiling system. It has recommended that the number of core loci expand from 13 to 24. Although few disagree that the system could use improvement, how they will go about choosing the additional core loci has been hotly debated recently. Some scientists, for example, worry that not enough experts have been involved in researching which core loci will be the best to include.
Regardless of the debate, however, using DNA to help solve crimes will continue to be a crucial tool in law enforcement's kit. During this week's lesson, you will discover some DNA basics, lab procedures, and real-world applications of DNA analysis.
All in the Family
DNA profiling relies on examining specific features of a person's genes. Crime investigators not only rely on one-to-one matches, but also on comparing evidence with possible close matches to relatives. So, why does using even a relative's DNA help solve crime? To find out, begin your own investigation into Heredity & Traits at the Genetic Science Learning Center. Focus on the right-hand side of the page to explore Chromosomes: The Vehicle of Heredity, starting with What Is A Chromosome? What is the relationship between chromosomes and DNA? What is an allele? Why can DNA be used to help determine degree of relatedness between people?
After watching the animation, learn more about How Scientists Read Chromosomes. Here, you will discover how size, banding patterns, and centromere positions help to identify chromosomes. Also, try your hand at Making a Karyotype by matching up the chromosomes. What kinds of features helped you match the pairs?
As you have discovered, DNA is very, very small. So, how is it analyzed to be able to compare samples? Stop in at the Gel Electrophoresis Virtual Lab to see one technique in action. What force is used to make the strands of DNA move through the gel? Why do you think strands of different length move at different rates through the gel? Why do scientists stain the gel? What kinds of tools, equipment, and materials are used to make the gel?
Check out another technique used in DNA analysis by visiting the PCR Virtual Lab. Here, you will find out how scientists target a small piece of DNA for study. What is the purpose of performing a PCR? What tools, equipment, and materials are needed to do it?
You have learned about chromosomes and analyzing DNA in the lab, but how can these techniques be used? Discover some real-world Applications at DNAi, provided by Dolan's DNA Learning Center. Begin by exploring the Human Identification module, using the navigation at the top of the page to then navigate within the module.
What does "STR" stand for? Why do you think STRs on different chromosomes are used rather than simply using 13 STRs on a single chromosome? In what way does the Hardy-Weinberg equilibrium principle relate to the probability of inheritance and genetic profiling?
Continue to Recovering the Romanovs module to investigate how DNA analysis helped solve the mystery of who was not the missing young daughter of the former Russian Tsar, Nicholas II. In what way did DNA analysis provide evidence for solving the case that other methods could not definitively prove?
In the Genes and Medicine module, meet some scientists using what has been learned about heredity and genes to help provide insight and possible treatments for genetic disorders and other illnesses, such as cancer. Why do scientists often use mice in genetic testing and manipulation for research in human disorders? How would you describe one of the feature stories and its potential to improve medicine in your future?
Of course, not only can DNA profiling be used for matching relatives and aiding medicine, it can also aid in better understanding Human Origins. How does using physical characteristics of fossilized remains compare to using DNA sequences for drawing our family tree? What role do mutations play in understanding our family tree? What is the significance of mitochondrial DNA?
DNA in Criminal Justice
Finally, learn more about the U.S. government's DNA Initiative, which aims to improve DNA technologies and assistance for solving criminal cases. Learn more About Forensic DNA, including its history, and gathering and analyzing evidence. What are some possible locations of DNA evidence and their sources? Why is securing crime scene integrity critical to an investigation? What are the basic steps for analyzing DNA evidence? How can DNA databases aid investigations?
Find current news in the e-edition about a criminal case in which DNA evidence may be useful. Glean as much detail as you can about the event, including the people involved. Based on the news story and what you learned in this lesson, write up an investigation plan as if you were the lead detective overseeing the case. Begin with assessing the scene, how your team would find and collect DNA evidence, how exactly that evidence would be processed from the scene to the lab, and how the DNA profile would be analyzed to try to identify a suspect or victim. What challenges would possibly arise in using CODIS or trying to match DNA to a possible relative? After completing your plan, follow the case as it actually unfolds. Did DNA evidence play any role in helping to solve it?