Biphasic patterns of diversification and the emergence of modules

Jay Mittenthal, Derek Caetano-Anollés, Gustavo Caetano-Anollés

Research output: Contribution to journalArticlepeer-review


The intricate molecular and cellular structure of organisms converts energy to work, which builds and maintains structure. Evolving structure implements modules, in which parts are tightly linked. Each module performs characteristic functions. In this work we propose that a module can emerge through two phases of diversification of parts. Early in the first phase of this biphasic pattern, the parts have weak linkage-they interact weakly and associate variously. The parts diversify and compete. Under selection for performance, interactions among the parts increasingly constrain their structure and associations. As many variants are eliminated, parts self-organize into modules with tight linkage. Linkage may increase in response to exogenous stresses as well as endogenous processes. In the second phase of diversification, variants of the module and its functions evolve and become new parts for a new cycle of generation of higher-level modules. This linkage hypothesis can interpret biphasic patterns in the diversification of protein domain structure, RNA and protein shapes, and networks in metabolism, codes, and embryos, and can explain hierarchical levels of structural organization that are widespread in biology.

Original languageEnglish (US)
Article numberArticle 147
JournalFrontiers in Genetics
Issue numberAUG
StatePublished - 2012


  • Biphasic hourglass
  • Competitive optimization
  • Diversification
  • Linkage
  • Module

ASJC Scopus subject areas

  • Molecular Medicine
  • Genetics
  • Genetics(clinical)


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