Application	LOF approach	Comments
General characterization of a gene with unknown function	Multiple approaches	Genetic knockout (for example, deletion of the open reading frame) will disrupt all gene functions and is most likely to provide the strongest phenotype
Study of essential genes	Knockdown or inducible knockout	Methods to perturb a subset of protein functions may also be useful (for example, SMIs)
Genes for which low levels of protein are sufficient to maintain function (for example, non-rate-limiting metabolic enzymes)	Knockout methods	Knockdown approaches result in residual wild-type protein and may not cause a phenotype in this case
Modelling drug action	Specific alleles or acute knockdown methods	Drugs may inhibit a subset of protein functions, requiring the generation of specific alleles to mimic the effect. Alternatively, all protein functions may be reduced similar to knockdown methods
Modelling disease-associated mutations	Specific alleles or non-coding mutations	Exact disease-associated mutations can be generated using genome-editing technologies