The invention relates to double-stranded RNA molecules in which each strand of said molecule possesses: (a) sufficient complementarity to a target mRNA molecule to facilitate cleavage thereof and (b) sufficient complementarity to the other strand of the double-stranded RNA molecule so as to form a stable duplex and in which at least one strand of said molecule possesses: (c) a seed region of complementarity to at least one seed site present in a 3 untranslated region of at least one target mRNA molecule. The invention also relates to an algorithm for the design of a double- stranded RNA molecule in which each strand of said molecule possesses: (a) sufficient complementarity to a target mRNA molecule to facilitate cleavage thereof and (b) sufficient complementarity to the other strand of the double-stranded RNA molecule so as to form a stable duplex and in which at least one strand of said molecule possesses: (c) a seed region of complementarity to at least one seed site present in a 3 untranslated region of at least one target mRNA molecule wherein said algorithm comprises the steps: (i) input a population of mRNA sequences transcribed from one or more genes of interest (ii) identify all subsequences of at least 12 nucleotides in length within the population of step (i) which are complementary to another subsequence of at least 12 nucleotides in length in the population (iii) determine a list of candidate bi-functional double-stranded RNA molecules, said list comprising the double-strand RNA duplexes comprising the two complementary subsequences of step (ii) and (iv) sort the list of candidate double-stranded RNA molecules of step (iii) based on their potential to cause translational suppression.Cette invention concerne des molécules dARN double brin, chaque brin de ladite molécule possédant : (a) une complémentarité suffisante avec une molécule dARNm cible pour faciliter son clivage et (b) une complémentarité suffisante avec lautre brin de la molécule dARN double
