Introduction:

A crime has been committed. Can you help us identify the perpetrators? You are now an honorary detective. Please help us investigate this bank robbery. The first step in an investigation is to interview eyewitnesses. Use our Crime Investigation Notebook and clues from an eyewitness account of the robbery to solve the mystery using the DNA evidence found at the scene of the crime.

Supplies:

• Crime Investigation Notebook
• supplies list will be completed soon
  
  

Activity 1: Observation of the Evidence
We need to sort and process the information supplied
by the eyewitness. In the pocket of the next notebook page is a worksheet with 2 parts. (If the pocket is empty just ask your teacher for a copy.) The first part has 7 questions which pertain to the eyewitness statement. Working in a small group fill the first part of the worksheet. You will keep this worksheet so go ahead and write directly on it. If you have any questions just refer back to the eyewitness statement. Discuss your answers
with the other groups.

We are in luck. The Banks’ video camera has captured the
crime on video. Included on the next 3 pages of this notebook are frames from the video. Working in small groups again try answering the questions in Part II of the worksheet. Discuss your answers with the other small groups.

We now have enough information to fill out a Crime Incident Data report. Blank report forms are in the pocket following the video frames. Use what you have learned from the eyewitness report and the video to fill out the report.

Congratulations detectives, you have now gathered the evidence. Now we need to process it and see what we can learn about the perpetrators. Remember the hat that fell off the bank robbers head? Well, we are in luckonce again, a strand of black, curly hair was discovered in the hat. This hair belongs to perpetrator #1. We took this piece of hair to the crime lab and found that the root was intact. Great, this means that DNA can be obtained. How does this work?

Take a look at the next page in the Crime Investigation
Notebook. In figure 1 you see what a strand of hair might look like under a microscope. One cell in that hair is shown in the highlighted circle. In figure 2, that cell is further magnified. Highlighted in this figure is the nucleus of the cell. The nucleus of the cell contains all the genetic information about the cell. This is what allows the cell to make new identical cells. In figure 3 this nucleus is further magnified. In figure 4 the chromosomes within the nucleus are visible. Each nucleus of a human cell (including a hair cell) contains 46 chromosomes arranged in 23 pairs. The
chromosomes are filled with very tightly coiled strands of DNA. Each person will have pretty unique DNA. Therefore, we can use the DNA found in the hair sample and compare it with the DNA of a suspect to see if they match.

Take a look at the back side of the page. Here you see the magnification of an individual chromosome. Each chromosome contains a set of genes (shown in black). The genes are segments of DNA that contain instructions that are responsible for specific traits. The gene containing information about a certain trait (like hair color) will occur on a specific location on a
certain chromosome. To understand how genes work on a chromosome proceed to Investigation 3, Chromosomes and Genes.

Activity 2: Chromosomes and Genes
We have now explored chromosomes and genes. We will now use this knowledge to construct some chromosomes with the genes of specific traits of the perpetrators. You should work with a partner or in a small group. For this part of the investigation each group needs the following supplies:

• Pencil
• Green, Red, Yellow, and Orange crayons
• Wooden dowel
• Chromosome building tray
• 1 long and 1 short gene (bead) in each of the 4 colors
• Investigation 3, Chromosomes and Genes worksheet

When you have collect these supplies, follow the instructions given in
the worksheet to assemble your chromosome building tray. The
proceed to build a sample chromosomes for each of the perpetrators.

DNA and DNA Fingerprinting
We now know that DNA is found in our individual genes. How is this DNA used to fingerprint an individual such as our bank robber? Well, DNA is a double helix. Look at the next page, Investigation 4, DNA and DNA Fingerprinting and in Figure 1 you will see a DNA double helix. The double helix can be separated by heating and a chemical process using enzymes can then cut the DNA into fragments. The size of these fragments will vary in individuals. We can separate these fragments into bands. The
visible pattern of bands is known as a DNA fingerprint. Look at figure 4. A detective has drawn a line from the evidence (E) blots to the suspect (S) blots. If there is a suspect blot for every evidence blot and no extras then we say they match.

Now is your chance to try it. For this exercise you will need:

• Dry erase marker
• Tissue or paper towel
• Ruler

Look at the back side of Investigation 4. Try investigations A and B. In each case you should draw a line from the evidence blot to the same place in the suspect row. Is there a blot there? Are there any blots in the suspect row that do no have a matching evidence blot? Question 2 is the same except now the DNA fingerprints are given horizontally. You should still draw lines from the evidence (E) blots to the corresponding space in the suspect (S) column. Try it. Do they match? Discuss your findings with the group. When you are finished and ready to continue, please wipe the page completely so that it will be ready for the next detective.