It's not random anymore

✍ Scribed by Lynn Helena Caporale

• Book ID: 101711754
• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 45 KB
• Volume: 30
• Category: Article
• ISSN: 0265-9247
• DOI: 10.1002/bies.20747

✦ Synopsis

The Varenna conference began with a talk by Mark Kirschner (Harvard), focused on evolution in multicellular organisms; Kirschner asked: for those phenotypic variations that are selected in evolution, is it easy or hard to achieve the useful variation that underlies the requisite developmental modifications? Kirschner pointed out that the probability of distinct phenotypic variations is not random ''because what already exists is not random'', and described core process of development that, while themselves highly constrained, have the effect of deconstraining changes around them, like variations on a theme. Such facilitated variation is enabled by ''exploratory processes'': bones are placed and then muscle cells and then nerves. The vascular system senses them and develops around them. If a gene affecting bone placement mutates, everything else does not have to mutate in just the right way; it all falls into place around the evolving bone. (3) Another, and conceptually not unrelated, evolvability trait discussed in several talks is modular genome organization. Frances Arnold (Caltech) described the role of modular ''recombinable elements'' (variable blocks surrounded by homologous sequence) in the evolution of protein families such as the cytochrome p450s.

Selection for improved survival enabled by more efficient exploration could, as Gunter Wagner (Yale) and others (4) point out, enable evolution of evolvabilty. From a general theoretical starting point, Michael Deem (Rice) observed