A<unk>  is either a<unk> tically modified organism that carries one or more<unk> s in its chromosomes that has been made less active or had its "expression" reduced or is the use of a reagent such as a short DNA or RNA (oligonucleotide) with sequence complementary to an active<unk>  or its mRNA  transcript.  This oligonucleotide will bind to this active<unk>  (or its transcripts) to decrease expression of a specific<unk> , copying the effects of such a<unk> tic modification. So far such organisms have been engineered chiefly for research purposes. Also known as<unk>  organisms or simply<unk> s, their most direct use is for learning about a<unk>  that has been sequenced, but has an unknown or incompletely known function, an experimental approach known as reverse<unk> tics. Researchers draw inferences from how the<unk>  differs from individuals in which the<unk>  of interest has not been made inoperative.<unk>  includes the processes of modifying an organism (as described above) or of using a reagent to suppress<unk>  expression, as in "knocking down a<unk> ."
Popular reagent-based methods of knocking down the expression of a<unk>  include suppression of translation using small interfering RNA (siRNA) or Morpholino oligos.
Gene knockdown
Chemical modification
Genetic engineering
Cre-Lox recombination
Dimroth rearrangement
Chemical engineering
Free radical reaction
Thermal depolymerization