Genetic predisposition to human disease: allele-specific expression and low-penetrance regulatory loci

The two alleles of a gene can be expressed at different levels, the extreme example being imprinting, a condition in which one allele is totally suppressed. Recently, subtle differences in the expression of the two alleles have been detected in numerous human genes and in a few cases, have been associated with a genetic predisposition to disease. The underlying mechanisms are largely unexplored.