cis versus trans effects

Main BJ, Bickel RD, McIntyre LM, Graze RM, Calabrese PP & Nuzhdin SV 2009 Allele-specific expression assays using Solexa. BMC Genomics 20:422.

• to test for cis-by-trans, we compared allelic imbalance in the heterozygote and the introgression within each W line (Figure 3)
• if all genes act additively, allelic imbalance in the heterozygote and introgression should be equal because the cis-regulatory elements for each allele and the trans-factors within each genotype are identical
• if allelic imbalance between these genotypes is not equal, that difference is due to cis-by-trans

• the regression coefficient is not significantly different from one (p = 0.5)
• there is no systematic cis-by-trans interactions detected within our sample population and selected genes
• this result, together with recent findings seems to be indicating that at least within Drosophila, epistasis may be rare or is small in magnitude [17]