The reduction can occur either through genetic modification or by treatment with a reagent such as a short DNA or RNA oligonucleotide that has a sequence complementary to either gene or an mRNA transcript.
Binding can occur either through the blocking of transcription (in the case of gene-binding), the degradation of the mRNA transcript (e.g. by small interfering RNA (siRNA)) or RNase-H dependent antisense, or through the blocking of either mRNA translation, pre-mRNA splicing sites, or nuclease cleavage sites used for maturation of other functional RNAs, including miRNA (e.g. by morpholino oligos or other RNase-H independent antisense).
In C. elegans research, the availability of tools such as the Ahringer RNAi Library give laboratories a way of testing many genes in a variety of experimental backgrounds.
[9][10] A different means of silencing exogenous DNA that has been discovered in prokaryotes is a mechanism involving loci called 'Clustered Regularly Interspaced Short Palindromic Repeats', or CRISPRs.
[11] CRISPR-associated (cas) genes encode cellular machinery that cuts exogenous DNA into small fragments and inserts them into a CRISPR repeat locus.
The CRISPR repeats are conserved amongst many species and have been demonstrated to be usable in human cells,[12] bacteria,[13] C. elegans,[14] zebrafish,[15] and other organisms for effective genome manipulation.
Another technology made possible by prokaryotic genome manipulation is the use of transcription activator-like effector nucleases (TALENs) to target specific genes.