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The look-ahead effect of phenotypic mutations - PubMed

  • ️Tue Jan 01 2008

Comparative Study

The look-ahead effect of phenotypic mutations

Dion J Whitehead et al. Biol Direct. 2008.

Abstract

Background: 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.

Results: 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.

Conclusion: 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 complettrait. Thus, errors allow protein sequences to "look-ahead" for a more direct path to a complex trait.

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Figures

Figure 1
Figure 1

The three alleles. The three alleles (or genotypes). The vertical lines in the genes indicate the number of key mutations required for the novel two-residue function. The fitness of the allele 1 increases if phenotypic mutations are taken into consideration.

Figure 2
Figure 2

Fixation probability of allele 2 (u2) vs. the selection coefficient s. Black is for u2(s, β), grey is for u2(s, 0). Solid lines are predictions according to Eq. (2) and (3), data points are for simulations with 109 repeats. N = 104, U=81910−8, β = 0.00019, T = 5 × 105. Error bars are standard errors.

Figure 3
Figure 3

Look-ahead effect (ξ) due to phenotypic mutations vs. the selection coefficient s. The solid line is for Eq. (5), dashes are for Eq. (6), dots are for Eq. (7), and data points are for simulations with 109 repeats. N = 104, U=81910−8, β = 0.00019, T = 5 × 105. Error bars are standard errors.

Figure 4
Figure 4

Look-ahead effect (ξ) due to phenotypic mutations vs. the selection coefficient s for different population sizes (N). Solid lines are from Equation (5), data points are for simulations with 108 repeats. U=81910−8, β = 0.00019, T = 5 × 105. Error bars are standard errors.

Figure 5
Figure 5

Look-ahead effect (ξ) due to phenotypic mutations vs. the selection coefficient s for different phenotypic error rates (β). Solid lines are from Equation (5), data points are for simulations with 108 repeats. N = 104, U=81910−8, T = 5 × 105. Error bars are standard errors.

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