Figure 1. Subtypes of allele-specific expression effects.

Allele-specific expression effects could potentially take on four basic forms that involve (1) equal expression of the maternal (red) and paternal (blue) alleles (biallelic), (2) complete silencing of one allele (monoallelic), (3) a bias to express either the maternal or paternal allele at a higher level (allele-specific bias), or (4) the expression of different isoforms from the maternal versus the paternal allele (allele-specific isoforms).