Patent ID: 8119608

Claim:
A method for inhibiting the expression of a target gene in a mammalian cell in vitro, comprising the steps of: a) introducing into said cell in vitro an isolated oligoribonucleotide consisting of two separate RNA single strands forming a double-stranded structure (dsRNA), wherein said dsRNA is prepared by: providing said two separate RNA single strands, wherein one strand of the dsRNA is complementary to an RNA transcript of at least part of said target gene and the other strand of the dsRNA is complementary to the first strand, and wherein the dsRNA is 21 base pairs in length, hybridizing said two separate RNA single strands, linking said hybridized strands, and b) maintaining the cell produced in step a) for a time sufficient to obtain degradation of an RNA transcript of said target gene by dsRNA-mediated interference, thereby inhibiting the expression of said target gene in said cell, wherein said separate RNA strands are further chemically linked, in addition to the cohesion caused by the nucleotide pairs in the double-stranded region, to reduce dissociation compared to non-linked RNA strands.