 Gene knockdown is achieved by preventing cells from making a targeted protein . Morpholinos can also modify the splicing of pre @-@ mRNA . Knocking down gene expression is a powerful method for learning about the function of a particular protein ; in a similar manner , causing a specific exon to be spliced out of a protein can help to determine the function of the protein moiety encoded by that exon or can sometimes knock down the protein activity altogether . These molecules have been applied to studies in several model organisms , including mice , zebrafish , frogs , and sea urchins . 
