Genetic Redundancies Enhance Information Transfer in Noisy Regulatory Circuits
Fig 2
Genetic redundancy amplifies information transfer in threshold genetic systems.
(A) Input/output distributions depicting information transfer. The input distribution (in yellow) is assumed to be uniform. Output distributions (in gray) illustrate the processing of the signal x, either through a single copy of the threshold device (left) or an array of multiple redundant copies (right). In the latter case, each unit of the array receives the same signal and the output y is the sum of all the individual responses (S2 Fig). Redundancy enlarges the alphabet of the response. This is reflected in the output distribution, and also in the linearization of the averaged stimulus-response profile (black curve). (B) (Left) Array of N threshold devices (circles) whose constituent units correspond to (1) a simple regulated unit, (2) a bistable circuit implemented with a positive feedback, and (3) an excitable circuit constituted by two interlinked positive and negative feedback loops. (Right) Dependence of mutual information (MI) with the number of units (N) for each of these systems relative to the case N = 1. A uniform signal distribution with mean equal to the threshold value was considered. MI does not increase with extra copies for noiseless units (independently of the type of unit; dashed line). See Materials and Methods for details on the modeling of each circuit.