 Morpholinos do not degrade their target RNA molecules , unlike many antisense structural types ( e.g. , phosphorothioates , siRNA ) . Instead , Morpholinos act by " steric blocking " , binding to a target sequence within an RNA and simply getting in the way of molecules that might otherwise interact with the RNA . Morpholino oligos are often used to investigate the role of a specific mRNA transcript in an embryo . Developmental biologists inject Morpholino oligos into eggs or embryos of zebrafish , African clawed frog ( Xenopus ) , sea urchin , and killifish ( F. <unk> ) producing morphant embryos , or <unk> Morpholinos into chick embryos at later stages of development . With appropriate cytosolic delivery systems , Morpholinos are effective in cell culture . Vivo @-@ Morpholinos , in which the oligo is covalently linked to a delivery dendrimer , enter cells when administered systemically in adult animals . 
