“…The pairing of homologs in somatic tissues enables regulatory elements on one homolog to exert their effects on the opposite homolog, resulting in genetic complementation in trans and the normal expression of a gene. Several genes have been observed to be subject to trans effects in Drosophila, including Ultrabithorax (Ubx) [125], yellow (y) [126,127], decapentaplegic (dpp) [128], cubitus interruptus (ci) [129], brown (bw) [130], engrailed (en) [131], eyes absent (eya) [132], Gpdh [133], hedgehog (hh) [134], pointed (pnt) [135], sex combs reduced (scr) [136], TMR of Abd-B [137], spineless (ss) [138], vestigial (vg) [139], white (w) [140], and wingless (wg) [141].…”