Abstract

How would you secretly mark a bank robber during a robbery? What could you do to ensure that the ethically grown cotton you grew and shipped off for weaving and garment making was used to make the shipment of shirts you received weeks later? When we want to tag and track something, we often use a barcode. From grocery store foods to FedEx packages, barcodes are a way of tagging and identifying items. The fact that barcodes can be unique and are easy to read are key features. Not all things can be barcoded though. A bank robber would certainly notice and discard a barcode. And a barcode would never stick to cotton throughout the process of weaving it into fabric, dyeing it, and turning it into clothing. What then can we use as a tiny invisible barcode that can still be unique and fairly easily "read"? The answer is DNA.

Usually, the term DNA barcode refers to a section of unique genomic DNA that can be used to identify, by PCR, one species from another species. You can learn more about DNA barcodes and how they were first developed from The History of DNA Barcoding video.

Companies have taken this same DNA barcode concept and created synthetic DNA versions sometimes referred to as molecular tags or DNA tags. These relatively short segments of DNA are synthesized and then applied to raw materials, everyday products, or even items at high risk of thievery. The tag can then be used to authenticate the material or product at every step of its journey by PCRing for the tag and confirming the result through sequencing or a similar technology. Watch the advertisement video from Applied DNA Sciences to see how they explain their CertainT DNA tagging system.

If you have access to a laboratory with molecular biology tools at a high school or local community college, you can make a science project out of exploring some of the challenges in making a molecular tagging system. You can explore questions like:

• How much of the DNA tag do you need to reliably detect it?
• Does the tag stay affixed to your product and detectable even in the face of harsh environmental or manufacturing conditions like being tumbled around, radiated under UV light, or exposed to acids and bases?
• What kind of system can you set up to reliably differentiate one tag from another so that you can create an infinite array of tags? Note: If you do not have access to a molecular biology laboratory, you could explore this question using just a computer.

To tackle one of the scientific questions that requires lab equipment you will at minimum need:

• The ability to create or purchase synthetic DNA sequences (the DNA tag) that you design as well as PCR primers to amplify the tag. A quick internet search will reveal many websites (most from primer manufacturing companies) that describe step-by-step how to design a good primer.
• A material or materials you which to tag. For simplicity, you may want to choose a material/product that does not have DNA such as plastic, rubber, or a mineral. Otherwise, you will need to make sure that your DNA tag and primers do not correspond to any sequences naturally found in the item(s) you are tagging.
• A PCR machine and reagents for amplifying the DNA tag.
• Electrophoresis equipment to visualize the DNA tag you applied and/or the ability to sequence your amplified DNA.

This area of science is constantly changing as different companies and research groups make new discoveries, improve their molecular tagging systems, and apply the results to real-world problems. Remember to do your background research to get up to speed on the field before diving into your experiments.