1. Now make a model of the bank robber's genes on the chromosome. Place the gene for the bank robber's (Perpetrator 1) GENDER on the chromosome as seen in FIG. 3. Next place the gene for his HAIR TEXTURE on the chromosome. Next place the gene for his HEIGHT on the chromosome. Next place the gene for HAIR COLOR. 2. Draw and color the pattern of genes on the chromosome for Perpetrator 1 in FIG. 4. FIG. 4 Now you will construct the chromosome for the Perpetrator 2, the accomplice. Remember you have some new information about hair color and texture. List the physical traits. FIG. 3 Gender Height Hair Color Hair Texture 1. Place the gene on the chromosome for HAIR COLOR first. Next place the gene for GENDER on the chromosome. Next place the gene for HAIR TEXTURE on the Chromosome. Next place the gene for HEIGHT on the chromosome. 2. Draw and color the pattern of the genes on Perpetrator 2's chromosome in FIG. 5. 3. Now assemble the accomplice's genes in the same order that you assembled Perpetrator 1. GENDER, HAIR TEXTURE, HEIGHT, and HAIR COLOR. 4. Draw and color the pattern of genes on this new chromosome in FIG. 6. 5. How are the chromosomes of the perpetrators alike?. 6. How are they different? FIG. 5 FIG. 6 1271WS3P INVESTIGATION 4 DNA AND DNA FINGERPRINTING INVESTIKITTS for KIDS Lab-Aids No. 1271 FORENSIC SCIENCE and DNA FINGERPRINTING If you were to look even closer at the gene, you would discover DNA, a chemical that can be analyzed from just about any cell in the body. In this investigation you will observe the structure of DNA and how it relates to Forensic Science. double helix base pairs enzymes electrophoresis Figure 1 VOCABULARY sequence complementary radioactive blot DNA fingerprint horizontal vertical fragments A model of DNA resembles a ladder that has been twisted into a structure know as a "double helix". The sides of the DNA ladder are composed of alternating deoxyribose sugar and phosphate molecules (see figure 1). The rungs of this ladder are made up of specific base pairs. The bases are adenine, thymine, guanine and cytosine. Adenine always pairs with thymine and guanine always pairs with thymine and guanine always pairs with cytosine. These sequences are repeated millions of times in every cell. The order of these pairs determines the unique characteristics of each individual. (See Figure 2). Figure 2 S S P C/G P S P T/A S S P A/T S P G/C S The double helix can be separted by heating. A chemical process using enzymes can cut the DNA into fragments. The size of these fragments will vary in individuals. They are then separted into bands by electrophoresis. This is then transferred onto a blot. Because certain bases will match complementary bases, radioactive probes can be used to attach to the DNA fingerprint. It resembles a UPC Bar Code you may see on grocery. Figure 3 1. Splitting and cutting DNA 2. Electrophoresis 3. Southern Blot 4. Radioactive probes 5. X-ray film made showing DNA fingerprints DNA fingerprints from evidence left at the scene of a crime can be compared to DNA fingerprints made from possible suspects. A match can positively identify the perpetrator. Likewise, when there isn't a match a suspect can be elimated. In the following activity, you will see two different kinds of DNA fingerprints. 1. The DNA agrees as seen by the lines in Figure 4. This is a VERTICAL match. DNA Fingerprint Figure 4 E: evidence S: suspect SINGLE MATCH S E