Position-effect variegation

Position-effect variegation is when something happens to a gene that changes how it works. In this type of variegation, the gene does not work as it normally does because it has been moved to a different place in the cells. Think about a part of a toy like a lego brick that has been accidentally moved to the other side of a toy - it won't work in the same way because it's in a different place. Position-effect variegation is like that - when a gene moves to a different place, the way it works changes.