Transvection

ScienceMatters @ Berkeley. Fly Guy: "In 1954, Nobel Laureate Ed Lewis, whom Levine calls the 'Einstein of flies,' proposed that a gene on one chromosome can directly affect the expression of its homologue gene on another chromosome, a process called transvection. However, the frequency of this 'crisscross' was unclear. Levine and Ronshaugen observed that, at least in the case of fruit flies, transvection is quite common.
'One possible explanation for transvection is maybe that it's used as a homeostasis mechanism,' Levine says. 'If an enhancer fails on one chromosome, the other chromosome can compensate. That way you make sure to get the right levels of expression.'"