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Table 1 Relationship between DNA letter distribution and information content

From: Skylign: a tool for creating informative, interactive logos representing sequence alignments and profile hidden Markov models

A% C% G% T% Information content
100 0 0 0 2.00
95 5 0 0 1.71
90 10 0 0 1.53
85 5 5 5 1.15
80 10 5 5 0.98
70 10 10 10 0.64
50 50 0 0 1.00
50 40 5 5 0.54
45 45 5 5 0.53
50 30 10 10 0.31
35 35 15 15 0.12
25 25 25 25 0.00
  1. Values assume a 4-letter DNA alphabet with a uniform background distribution. The maximum information content under these conditions is 2.0, for an invariant distribution. The minimum value is 0.0, achieved when the letter distribution matches the background. Note that small perturbations away from invariance result in large reductions in information content.