Each individual DNA is unique. DNA contains short regions with patterned repeats of the four DNA bases, labeled A, G, C and T. Some individuals may have 10 repeats while others have 11. An activity for students may be to create mathematical challenges, calculating possible variations in the number of repeats when comparing one region of DNA. One region would show only two possible variations, while 15 regions would provide 32,768 variations.
Teachers can include activities that introduce students to methods used to find genetic variability in different individuals. Restriction digest is one simple method. It uses the ability of restriction enzymes to identify and cut regions of a DNA molecule into smaller fragments that can be measured. You can provide pictures of various DNA fragments, from different hypothetical individuals, and compare them to determine if they are from the same individual.
Electrophoresis is a method that separates DNA fragments on agarose gel by size, using electrical current. The process follows restriction digest to determine sizes of enzyme cut fragments. Food colors or other available dyes provide a good demonstration of different sized DNA fragments. Students can observe size separation as individual dye colors separate on agarose gel. Mixing various colors before loading the gel will represent DNA variability.
Students can investigate a crime scene constructed in the classroom, collect possible DNA evidence and compare DNA fingerprints to solve the mystery. Examples of DNA fingerprints are available online or a teacher can re-create possible DNA fingerprints as evidence. Selected students can represent the suspects or choose other teachers to participate. Crime scene investigation is the underlying purpose for forensic DNA fingerprinting techniques.