by Merry Youle — Most eu­kary­otes pos­sess an RNA in­ter­fer­ence sys­tem (RNAi) that they use to reg­u­late gene ex­pres­sion and to de­fend against viruses and other mo­bile el­e­ments. How­ever, some bud­ding yeasts, such as Sac­cha­romyces cere­visiae, ap­pear to get along just fine with­out it even though RNAi has ben­e­fited other yeasts by si­lenc­ing trans­posons…