A gene knockout (KO) is a genetic technique in which an organism is engineered to carry genes that have been made inoperative. However, KO can also refer to the gene that is knocked out or the organism that carries the gene knockout. Those organisms carrying such genes are known as knockout organisms or simple knockouts, they are used in assigning function to specific gene having unknown function that has been sequenced. In summary, KO is an organism in which a single gene of choice or interest is either inactivated or knockout in a manner that leaves all other genes unaffected and the best way to delineate the function of gene by homologous recombination method.
A gene knockout (KO) is a genetic technique supplemented with biotechnological tool. The KO technique is essentially the opposite of gene knock in. Knocking out two genes simultaneously in an organism is known as a double knockout (DKO). Similarly, the terms triple knockout (TKO) and quadruple knockouts (QKO) are used to describe three or four knocked out genes, respectively. However, one needs to distinguish between heterozygous and homozygous KOs. In the former, only one of two gene copies (alleles) is knocked out, in the latter both copies (alleles) are knocked out.
Gene knockout strategy, being reverse genetics tools, used to determine the target gene function by gene tagging, mutagenesis and homologous recombination and followed by studying the consequences of altered phenotype, thus produced recognizable gene function. Knockout organisms or simply knockouts are used to study gene function, usually by investigating the effect of gene loss. Researchers draw inferences from the difference between the knockout organism and normal individuals. Gene knockout technologies have become invaluable experimental tools for modelling genetic disorders, assigning functions to genes, evaluating drugs and toxins and for helping to found answers of fundamental questions in basic and applied research.
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