Patent ID: 8309533

Claim:
A method of inhibiting expression of a target allele in a cell comprising at least two different alleles of a gene, the method comprising (i) introducing to the cell shRNA comprising a duplex stem comprising an antisense stem portion having a length of 21 nucleotides and a sense stem portion, wherein said shRNA is targeted to the target allele, and wherein the target allele is a gain-of-function mutant allele, and (ii) enhancing the asymmetry of said stem, wherein the asymmetry is enhanced by lessening the base pair strength between base pairs at the 5′ end of the antisense strand portion and corresponding base pairs in the 3′ end of the sense stem portion, wherein the base pair strength is less due to introduction of a single mismatched base pair between the 5′ end of the antisense stem portion and the 3′ end of the sense stem portion at position 3 from the 5′ end of the antisense strand portion.