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Figure 2 | BMC Bioinformatics

Figure 2

From: Evolution of biological sequences implies an extreme value distribution of type I for both global and local pairwise alignment scores

Figure 2

Computing of the probability that the amount of information shared by two sequences, S , is lower than a threshold s. Given an initial sequence a, we can envisage different scenarios for its evolution into another sequence b. In a first step (Step 1), an elementary probability is computed by taking into account the evolution of just one residue (here a1 into b1). Considering one possible evolutionary scenario (Step 2), residues are considered as independent and the probability is the product of elementary probabilities for each positions aligned in this scenario, with approximations in the asymptotic limit of long sequences. The final probability (Step 3) is then estimated by taking into account all the possible evolutionary scenarios.

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