DNA Fingerprinting

From high- profile trials to popular TV shows, numerous events have imprinted on our collective psyche the fact that DNA evidence can be used to solve crimes. But the technique has extensive uses that go far beyond forensic science. You may even owe tonight’s dinner, in part, to DNA fingerprinting.

My curiosity about this subject was piqued when I came across a recent newspaper report that talked about how DNA fingerprinting is being used in India to identify different varieties of basmati rice. The report mentioned a hotel that buys around200 tons of basmati rice per year. The hotel’s chefs found it difficult to cook the rice properly because each type of basmati rice has different soaking times and cooking properties. A visual inspection is of limited use because all the varieties look nearly the same. They decided to solve this problem by working with the rice’s producer to certify each bag of rice using DNA fingerprinting; the chefs then use the information to help them determine the proper cooking parameters.

How Does It Work?

DNA sequences are extremely long, and comparing an entire DNA sequence with another would be hard to do. Fortunately, though, about99% of human DNA is identical from one person to the next. The1% that’s different includes several frequently repeating sequences; the number of repeating sequences in any given position on a chromosome is different for each person.

Therefore, in DNA fingerprinting, fragments of DNA are extracted and a collection is created that is unique for each person. There are several techniques for doing so; they differ mainly in how the fragments are extracted and how they are converted into a form that can be analyzed for identification.

While human DNA fingerprinting has numerous uses in law and forensics— from verifying paternity to identifying murder suspects— this technique also applies to other organisms. Plants, animals, and even bacteria have unique DNA fingerprints. An increasing range of applications makes use of this fact. For example:

Fighting Disease: The big problem in treating bacterial infections using antibiotics is the fact that, over time, bacteria become resistant to the antibiotics, thereby making the treatment ineffective. DNA fingerprinting is being used to identify antibiotic- resistant strains. This helps doctors to select an antibiotic other than the one to which the bacteria are resistant, or consider a different type of treatment altogether. The Centers for Disease Control( CDC) has been using DNA fingerprinting successfully for controlling the spread of tuberculosis( caused by Mycobacterium tuberculosis) for the past few years.

Fighting Foodborne Illnesses: E. coli is a type of bacteria that lives in the intestines of humans and animals and is generally harmless. However, there are a few strains of E. coli that are quite dangerous— such as O157: H7 ( sometimes found as a contaminant in beef), which produces a powerful toxin and can cause severe illness. By using DNA fingerprinting, this harmful strain can be identified easily if it’s present in food. After a major outbreak of this E. coli strain in1993, the CDC created PulseNet, a national network of laboratories that performs DNA fingerprinting on food- borne bacteria. PulseNet has been instrumental in stopping outbreaks by quickly identifying the strain in contaminated food after comparing it against known patterns.

Fighting Fraud: How do you know that the contents of the bottle of wine or the bottle of medicine you are about to consume is authentic? Wine producers are using DNA fingerprinting to ensure that the correct grapes have gone into the making of the wine, thereby guaranteeing its authenticity. Pharmaceutical manufacturers are working on using DNA fingerprinting for labeling medicines so that counterfeits can be detected more readily. Experts now think that DNA fingerprinting, when combined with rapid detection methods, can give rise to better authentication tools than the ones in use today.

Genography: Not to be confused with geography, genography( or genetic anthropology) studies the migration patterns of humans over long periods of time. The National Geographic Society has embarked on an ambitious5- year project that will use DNA fingerprinting to map the journey of human beings since prehistoric times as they migrated to various parts of the globe. They are relying on the fact that some parts of the DNA, called“ genetic markers,” are passed down generation to generation without modification. Using these markers, the project attempts to trace the movement of humans over the ages and the path of human evolution from their prehistoric roots in Africa.

As the field of genetic engineering increases in popularity, the range of applications for DNA fingerprinting is likely to widen. Just as with conventional fingerprinting, there is always some margin of error, and ethical questions abound, particularly when humans are involved. But the evidence so far suggests that the potential benefits far outweigh the risks, and the future of DNA fingerprinting looks bright. — Rajagopal Sukumar

Guest author Rajagopal Sukumar lives in Chennai, India and serves as the Chief Knowledge Officer( CKO) of a software consulting company that specializes in the global delivery model. You can read his personal blog at www. sastwingees. org.