Additional File 1.

Gene-gene and gene-environment interaction model. Contains the Visual Basic macro (Twincal), input and output datasheets and charts used to calculate the solutions described in the text. The program is run by entering parameters in the 'Inputs' sheet and clicking on the 'Run' button. Note that for the final chart ('fe') the number of categories on the horizontal axis changes depending on the environmental input parameters ε and PAF^E_e. If these parameters are changed it is therefore necessary to delete the lower part of the output sheet prior to running the model and, after the run, to redraw the chart using the source data option from the chart. All other charts are drawn automatically. The line γ_max = γ_min is calculated exactly for the chart 'fe' but is approximated in the charts 'pgdz' and 'pgdzneg' using Newton's method and an initial guess for f_ge (f0) and step (fet). For some input parameters it may be necessary to change these values by editing the Visual Basic code (Twincal) to obtain a valid solution.

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Wallace Theoretical Biology and Medical Modelling 2006 3:35   doi:10.1186/1742-4682-3-35