Daily Archives: June 27, 2009

The Increasing Hydrophobicity Effect

I have argued that the genetic code may have been designed to exploit the mutagenic bias that exists as a consequence of cytosine deamination. In my original analysis, I noted that the genetic code uses cytosine deamination to channel mutations such that they sample from an pool of amino acids that is almost exclusively hydrophobic (IHE or Increasing Hydrophobicity Effect). Furthermore, this pool is biased toward facilitating secondary structure formation. If coupled with carefully chosen initial proteomes, the potential exists that the first major evolutionary steps subsequent to the originally designed state where rigged such that the mutational bias could untap secondary designs that were front-loaded into the original state. For example, this might mean that something like the evolution of multicellularity (and perhaps more) was designed through this biased mutagenic effect.

The first step in testing this hypothesis is to determine whether the IHE plays out in evolution. Since the genetic code is universal, we might expect to see residual traces of this effect even if the sole intention of the design was to guide the first major evolutionary steps. Two extensive analyses have indeed uncovered the IHE in action (although neither paper makes the connection I did in my original analysis).

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Bacteria Plan Ahead, Anticipating Future Events

Just as humans have learned to connect dark clouds with rain, so too have bacteria and yeast learned to use one event to predict the arrival of another.

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