Phenotype is influenced by nature, nurture and noise

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Phenotype is influenced by nature, nurture and noise

http://www.medicalnewstoday.com/medicalnews.php?newsid=31496

04 Oct 2005

Geneticists have debated for decades the relative importance of

nature versus nurture in determining how an animal looks and behaves,

and now UCSD scientists report that noise could also be an important

factor in determining phenotype.

In a paper in Proceedings of the National Academy of Sciences

released online Sept. 30, the scientists led by bioengineering

professor Jeff Hasty reported that a newly developed computer model

shows that a combination of unscripted biochemical variations, or

noise, leads to oscillations in gene regulation that couldn't

otherwise be predicted. Such noise is routinely described by cell

biologists who record large phenotypic differences between supposedly

identical cells in a single flask of growth medium.

The mental picture most biologists have of a cell is of a smoothly

running Swiss watch, " said Hasty. " But our results and the findings

of other theorists and computational biologists are proving

otherwise. The fine-grain fluctuations we see in the genetic

regulation within single cells may lead to new insights about

variability at the level of a fly, cat, or human. "

Changes in a cell's phenotype may be triggered by environmental

factors, by programmed genetic instructions, or more subtly by built-

in delays in biochemical pathways that generate oscillations,

sometimes in 24-hour circadian periods. Hasty, graduate students

Dmitri Bratsun and Dmitri Volfson, and post-doctoral fellow Lev. S.

Tsimring modified the Gillespie algorithm, a well known computer

model of cellular reactions, by factoring in intrinsic noise and

delays. Using the modified Gillespie algorithm and sophisticated

mathematical analyses of sets of biochemical reactions, the team

discovered how the combination of intrinsic noise and biochemical

delays also generates oscillations in phenotype.

" We think an analysis of such fine details of gene regulation

explains not only the observed variability of cells, but also, in a

larger sense, why identical twins don't necessarily have identical

fingerprints, " said Hasty. " Given that every potential feature of an

organism is ultimately determined at the genetic level, it is

important to zoon in on the noisy details of gene expression to

explain the variability that we couldn't otherwise account for. "

University of California - San Diego

http://www.ucsd.edu