Patent ID: 7550264

Claim:
A method for performing multiple rounds of synthesis of at least one sRNA molecule, comprising: a) providing at least one first round single stranded cDNA molecule having a 5′ end and a 3′ end; b) attaching an oligodeoxynucleotide tail onto the 3′ end of said first round cDNA molecule; c) annealing to said oligodeoxynucleotide tail a single stranded promoter template comprising a first RNA polymerase recognition sequence and at least a second different RNA polymerase recognition sequence 3′ to said first recognition sequence, wherein said single stranded promoter template is not extendable with DNA polymerase; d) extending said oligodeoxynucleotide tail such that said single stranded promoter template is converted into a first RNA polymerase promoter and at least a second RNA polymerase promoter 3′ to said first promoter; e) initiating a first round of RNA transcription using an RNA polymerase which recognizes said first RNA polymerase promoter to produce at least one first round sRNA molecule; f) synthesizing at least one second round single stranded cDNA molecule from said first round sRNA molecule, said second round single stranded cDNA molecule having 5′ and 3′ ends; g) degrading said first round sRNA molecule; h) annealing a single stranded promoter oligonucleotide complementary to said second different RNA polymerase recognition sequence such that a second RNA polymerase promoter is formed; and i) initiating a second round of RNA transcription using an RNA polymerase which recognizes said second RNA polymerase promoter to produce at least one second round sRNA molecule, thereby performing multiple rounds of synthesis of at least one sRNA molecule and producing multiple sRNA copies.