Clone-specific monoallelic expression and tissue-scale allelic imbalance. Allelic imbalance has been noted for a variety of genes in different tissues and is typically attributed to either parent-of-origin imprinting or to cis-regulatory variants. Skewed random monoallelic expression (RMAE), when one allele is preferentially chosen for expression, could also result in a tissue-wide allelic imbalance. In a traditional view (left) the expression level varies between the two alleles, with the paternal (pat) allele contributing more. This is uniformly true among the cells in the tissue. By contrast, in the scenario depicted at right, a difference in the relative abundance of cells with different RMAE states results in a tissue-scale allelic imbalance. Mat, maternal; Pat, paternal.