Provided are an improved double-stranded nucleic acid molecule involved in gene expression control mediated by a gene silencing mechanism, a method of producing the molecule, and a pharmaceutical composition comprising the double-stranded nucleic acid molecule. The double-stranded nucleic acid molecule for gene expression control comprises an antisense strand having a length of 18 to 28 nucleotides and a sense strand including a complementary moiety composed of a sequence sufficiently complementary to the antisense strand and a protruding single-stranded 5′-end moiety having a length of 2 to 100 nucleotides. The sense strand and the antisense strand form base pairs via the complementary moiety. The method produces such a double-stranded nucleic acid molecule, and the pharmaceutical composition contains such a double-stranded nucleic acid molecule as an active ingredient.
