FT. LAUDERDALE, Fla. _ Judging by the number of attendeeswho swarmed around the speaker after his talk, the biggest draw atWednesday morning's session here was "Fractals, DNA and theevolution of biologic complexity."
Ary Goldberger, who presented this still-trendy topic, is a clinicalcardiologist at Boston's Beth Israel Hospital, where he applies fractalanalysis in his daily bedside practice. He is also a founder of themodern resurgence of fractal theory, which peaked in the late 1980s,and is now enjoying a second coming.
But the speaker added, as "truth in advertising," that the fractalconcept has about as many skeptics as it does adherents.
Goldberger defines fractals by analogy to the wrinkles of coastlinesor mountain-range skylines, or the microscopic irregularities inprinted lines. Each wrinkle, he said, can be magnified to contain theentire image of the coastline or skyline, and each of those sub-wrinkles again iterated and reiterated.
Thus, in mammalian physiology, each tendril of the ever-branchingbroncho-pulmonary tree or neuron-dendrite divisions and sub-divisions, or the coronary arteries smaller and smaller vesselsfeeding the heart, embody the entire structure in each of its branchesand twigs, he explained.
He also compared fractal's ever-iterating branches to the federalbureaucracy.
More conceptually," Goldberger explained, "A fractal is an objectthat geometrically has cell similarity; that is, its small-scalecomponents resemble in some statistical way the larger-scalestructure.
"Our group," he told his audience, "was one of the first to applyfractals to biology in clinical medicine. It was our work in the 80sthat led to current interest in applying fractals to normal physiologyand pathology."
Goldberger directs Beth Israel's arrhythmia and bioengineeringlaboratory, which, he said, "is a signal-processing type of lab. But what we do goes beyond signalprocessing.
"We use the fractal concept," he explained, "in part, to try toquantify the normal physiological system. The breakdown of thesefractal properties is a way of indicating that the system is at risk ofdisease, or drug toxicity or the aging process."
At the level of biotechnology, Goldberger told BioWorld Today, welook at the genome, to distinguish between coding DNA and non-coding DNA. The latter," he pointed out, "accounts for 97 percent ofthe human genome, and tends to get ignored as junk DNA."
Working from sequences in GenBank, he continued, "We usefractals in a practical way as a gene finder, in particular for longergenes that are adapted to identify unknown sequences. that occupyso much of the human genome. That's an exciting prospect. becausethere may be a whole other set of another language, or languages, orcodes, that may be important in directing some complex interactionsamong genes. And that's very much of a wide-open territory."
Goldberger's reference to "language" is more than an analogy; it'sbehind a method he calls "gene walking," by going down a DNAsequence one base pair after another. Walking "up" for each AT, and"down" for each AG creates a diagrammatic wrinkled map of thegene sequence corresponding to fractally iterated self-similar cells.
Then by counting each base, and ordering the compilation byfrequency of occurrence, he generates a "language" by which tofractally analyze the given genomic sequence.
In ordinary written English, Goldberger pointed out, omittingoccasional letters doesn't destroy the meaning. On the other hand,the Morse code admits of no such redundancy. A single code symbolleft out, he observed, "can mess up the entire message." Ditto in theDNA code; a point mutation can upset the total gene message.
"We just recently concluded a study [in press] of the entireGenBank," Goldberger said, "consisting of all its 33,301 coding and29,453 non-coding sequences. It confirms our results."
"The exciting part of the work," he said, "is that it suggests there is ahidden structure to non-coding DNA, an underlying language orlanguages that may be very important biologically, and has yet to beaddressed. That may open up a whole new world of control for theway that genes really work."
He and his fractal group are now pursuing what this hidden DNAlanguage is, and how the non-coding sequences may relate to signaltransduction of the control of information. "Now that we'vecharacterized some of these properties," he concluded, "we're tryingto give them some biological form and meaning." n
-- David N. Leff Science Editor
(c) 1997 American Health Consultants. All rights reserved.