The look-ahead effect of phenotypic mutations

TL;DR

This paper proposes that transcription and translation errors can facilitate the evolution of complex traits by allowing intermediate mutations to be phenotypically expressed, thus enabling populations to 'look ahead' and acquire advantageous traits more efficiently.

Contribution

It introduces a population-based model demonstrating how phenotypic mutations enable the evolution of complex traits through a look-ahead effect.

Findings

Errors in transcription and translation can promote intermediate mutations.

Phenotypic mutations increase the fixation probability of advantageous traits.

The model shows a pathway for complex trait evolution via phenotypic 'look-ahead'.

Abstract

The evolution of complex molecular traits such as disulphide bridges often requires multiple mutations. The intermediate steps in such evolutionary trajectories are likely to be selectively neutral or deleterious. Therefore, large populations and long times may be required to evolve such traits. We propose that errors in transcription and translation may allow selection for the intermediate mutations if the final trait provides a large enough selective advantage. We test this hypothesis using a population based model of protein evolution. If an individual acquires one of two mutations needed for a novel trait, the second mutation can be introduced into the phenotype due to transcription and translation errors. If the novel trait is advantageous enough, the allele with only one mutation will spread through the population, even though the gene sequence does not yet code for the complete trait. The first mutation then has a higher frequency than expected without phenotypic mutations giving the second mutation a higher probability of fixation. Thus, errors allow protein sequences to ''look-ahead'' for a more direct path to a complex trait.