Friday, July 22, 2005

More on the landscape....   posted by Razib @ 7/22/2005 12:23:00 AM


...We show that it is the consequence of a particular form of epistasis, which we designate sign epistasis. Sign epistasis means that the sign of the fitness effect of a mutation is under epistatic control; thus, such a mutation is beneficial on some genetic backgrounds and deleterious on others. Recent experimental innovations in microbial systems now permit assessment of the fitness effects of individual mutations on multiple genetic backgrounds. We review this literature and identify many examples of sign epistasis, and we suggest that the implications of these results may generalize to other organisms. These theoretical and empirical considerations imply that strong genetic constraint on the selective accessibility of trajectories to high fitness genotypes may exist and suggest specific areas of investigation for future research.

So the deviation is flipping between positive and negative and deep fitness valleys separate peaks, impeding the exploration of the adaptive landscape. At least that's how I read it....

Related: Through the rugged roads of gene land.