A movement in science to catalog all life on Earth by a simple standardized genetic tag similar to stores labeling products with unique barcodes could be turning into the definitive apples and oranges conundrum.

According to a new Brigham Young University study, the effort that holds the promise of, among other things, fool-proof detection of food-borne bacteria, stronger defenses against disease-causing insects and improved monitoring of U.S. borders also has the substantial risk of inaccuracy.

Researchers at BYU report in the prestigious Proceedings of the National Academy of Sciences that the DNA method is as prone to mistakes as the scanners at a grocery store that can ring up grapes when you've punched in onions.

Hojun Song, a postdoctoral BYU researcher, came across the potential for ringing up the wrong match while completing a paper based on his genetic analysis of grasshoppers.

Several problematic nuclear mitochondrial pseudogenes or "numts," as scientists call these bits of inactive genetic code, surfaced in the study that were similar to results from analyses of cave crayfish. Song compared data, and the published paper is the result.

"I recognize that some who do DNA barcoding may be upset by this study, but that is the nature of science," Song said. "Building a genetic library of all life is a great goal, but we need to be careful to pay attention to the data that go into that library to make sure they are accurate."

The $150 million Barcode of Life project to build on the 400,000 species that have been "barcoded" to date warrants a more careful execution if it is to serve its ultimate purpose, according to the BYU team.

"It is like attempting to assemble a library on American history without bothering to filter out books on Forrest Gump and Harry Potter," said Michael Whiting, professor of biology and co-author of the study.

At this point, proponents of DNA barcoding seek to establish a short genetic sequence as a way of identifying species in addition to traditional approaches based on external physical features.

Today, biologists still use Linnaean taxonomy as the foundation of scientific classification founded in the 1700s. Old methods won't do, given that only a fraction of the estimated 5 million to 30 million species on Earth have been named.

If the bugs can be worked out of plant barcoding, amateur biologists and other nonexperts will be able to take a small portable device, capable of reading a plant's genetic barcode, into species-rich areas of the world for their plant composition to be established.

DNA barcoding provides an additional taxonomic tool when traditional observation techniques are unreliable. It is also helpful in revealing cryptic species — those that look the same but are in fact genetically different.

This new approach requires only part of a sample. A feather left behind by a bird struck by an airliner, for example, would be enough to indicate its species and clue officials how to prevent future collisions. And organisms can be identified no matter the stage of life.

According to the BYU study, contamination is often difficult and time-consuming to identify, which in turn leads to overestimating the number of species in a sample by more than several hundred percent.

E-mail: jthalman@desnews.com