====== Definitions for commonly used terms ======

**Dataset**-a dataset includes all the screens associated with a particular publication or pre-publication document. A single publication may have 1-100s of screens associated with it.

**Screen**-a set of gene level quantitative scores derived from a single experiment. Each screen is assigned a number followed by the PubMed ID (e.g. 1-PMID26627737) to ensure publications with mulitple screens have a unique identifier for each individual screen.

**Negative Selection Screen**-Screen for identifying genes whose perturbation results in cells not surviving the selection mechanism. Typically, the associated phenotype is “viability” or “resistance” and the mutants are underrepresented/depleted after selection. This fitness screen may be used to determine gene essentiality. May also be referred to as a dropout screen.

**Positive Selection Screen**-Screen for identifying genes whose perturbation results in cells surviving the selection mechanism, e.g drug exposure. Typically, the associated phenotype is “viability” or “resistance” and the mutants are overrepresented/enriched after selection. This fitness screen may be used to detect drug resistance and identify drug targets. Also known as an enrichment screen.

**Phenotype Screen**-Screen for identifying genes whose perturbation results in other non-fitness phenotypes, such as altered nuclear size or detection of a selectable marker for measuring activity of a particular pathway.

**CRISPRn/Knockout Library **-A gRNA library designed to generate knockout cells or animals with loss-function mutations within the targeted genes.

**CRISPRa/Activation Library **-A gRNA library used in conjunction with a modified Cas enzyme fused to protein domains that turn gene expression on, thereby activating gene expression of target genes.

**CRISPRi/Inhibtion Library **-A gRNA library used in conjunction with a modified Cas enzyme fused to protein domains that turn gene expression off, thereby repressing or inhibiting gene expression without knocking the gene out.

**Analytical Method **-The statistical or computational method used by the authors to determine which genes in their screen represent hits. These can range from straight-forward read counts to very complex scoring systems with associated confidence values. For a detailed list of the analytical methods currently in ORCS and the relevant references for these methods go [[orcs:controlled_vocabulary6|here]]