 A morpholino , also known as a morpholino oligomer and as a phosphorodiamidate morpholino oligomer ( PMO ) , is type of oligomer molecule ( colloquially , an oligo ) used in molecular biology to modify gene expression . The molecular structure has a backbone of <unk> rings and phosphorodiamidate linkages . Morpholinos block access of other molecules to small ( ~ 25 base ) specific sequences of the base @-@ pairing surfaces of ribonucleic acid ( RNA ) . Morpholinos are used as research tools for reverse genetics by knocking down gene function . They are being studied for application in medicine . 
