  We study the correlation of the occurrence of coronary heart disease (CHD)
with the presence of the single-nucleotide polymorphism (SNP) at the -308
position of the tumor necrosis factor alpha (TNF-$\alpha$) gene. We also
consider the influence of the occurrence of type 2 diabetes (t2DM). Using
Bayesian inference, we first pursue a bottom-up approach to compute the working
hypothesis and the probabilities derivable from the data. We then pursue a
top-down approach by modelling the signal pathway that causally connects the
SNP with the emergence of CHD. We compute the functional form of the
probability of CHD conditional on the presence of the SNP in terms of both the
statistical and biochemical properties of the system. From the probability of
occurrence of a disease conditional on a given risk factor, we explore the
possibility of extracting information on the pathways involved in the
occurrence of the disease. This is a first study that we want to systematise
into a comprehensive formalism to be applied to the inference of the mechanism
connecting the risk factors to the disease.
