Patent ID: 8741569

Claim:
A method for normalizing a population of different small nucleic acid species of varying abundance, wherein each small nucleic acid species is less than thirty nucleotides long, the method comprising, ligating a 3′ adapter and a 5′ adapter, respectively, to the 3′ and 5′ ends of at least some of the small nucleic acids in the population to form a multiplicity of different double adapter-modified molecules, wherein the adapters comprise a 3′ adapter comprising a first primer-binding site, and a 5′ adapter comprising a second primer-binding site; amplifying at least some of the multiplicity of different double adapter-modified molecules with a formulated relative concentration of primers to generate a normalized population, wherein the formulated relative concentration of primers comprises a multiplicity of primer species each comprising different degenerate sequences at their respective 3′-ends and a corresponding universal primer species, wherein at least one of the degenerate sequences comprises one, two, three, four, five, or six nucleotides, wherein the concentration of the universal primer species is at least ten times greater than the concentration of any one of the primer species comprising a degenerate sequence, and wherein the concentration of the universal primer is greater than the total concentration of the multiplicity of primers comprising different degenerate sequences, and wherein the amplifying comprises a polymerase chain reaction.