Gene knockout
A gene knockout, isgenetically engineered organism that carries one or more genesits chromosomes that has been made inoperative. So far such organisms have been engineered chieflyresearch purposes. Also known as knockout organisms or simply knockouts, their most direct use islearning aboutgene that has been sequenced, but has an unknown or incompletely known function. Researchers draw inferences from howknockout differs from individualswhichgeneinterest has not been made inoperative. Knockoutalsoprocesscreating such an organism, as"knocking outgene."Method
Knockoutaccomplished throughcombinationtechniques, beginning intest tube withplasmid,bacterial artificial chromosome or other DNA construct,proceedingcell culture. Individual cellsgenetically transformed withconstruct and--for knockoutsmulti-cellular organisms--ultimately fused withstem cell fromnascent embryo .
The constructengineeredrecombine withtarget gene, whichaccomplished by incorporating sequences fromgene itself intoconstruct. Recombination then occurs inregionthat sequence withingene, resulting ininsertion offoreign sequencedisruptgene. With its sequence interupted,altered genemost cases will be translated intononfunctional protein, if ittranslated at all.
Because recombination israre event incasemost cellsmost constructs,foreign sequence choseninsertion usually isreporter. This enables easy selectioncells or individualswhich knockout was successful.
In diploid organisms, which contain two allelesmost genes,may as well contain several related genes that collaborate insame role, additional roundstransformationselectionperformed until every targetted geneknocked out.
Compare: knock-in; knockdown
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