extrinsic genotype In an experiment where shha is targeted by MO1 and shhb is overexpressed from a transgenic expression construct, the extrinsic genotype captures the altered expression status of these two genes. A notation for representing such a genotype might describe this scenario as: shha<MO1-1ng/ul>; shhb<pFLAG-mmusShhb> This notation parallels those used for more traditional 'intrinsic' genotypes, where the affected gene is presented with its alteration in angled brackets < >. In the extrinsic genotype shown here, the variation in shha is affected by a specific concentration of an shha-targeting morpholino (instead of a mutation in the shha gene). And the variation in shhb is affected by its overexpression from a pFLAG Shhb expression construct. expression genotype experimental genotype A specification of the known state of gene expression across a genome, and how it varies from some baseline/reference state. An extrinsic genotype describes variation in the 'expression level' of genes in a cell or organism, as mediated by transient, gene-specific experimental interventions such as RNAi, morpholinos, TALENS CRISPR, or construct overexpression. This concept is relevant primarily for model organisms and systems that are subjected to such interventions to determine how altered expression of specific genes may impact organismal or cellular phenotypes in the context of a particular experiment. The 'extrinsic genotype' concept is contrasted with the more familiar notion of an 'intrinsic genotype', describing variation in the inherent genomic sequence (i.e. 'allelic state'). In G2P research, interventions affecting both genomic sequence and gene expression are commonly applied in order to assess the impact specific genomic features can have on phenotype and disease. It is in this context that we chose to model 'extrinsic' alterations in expression as genotypes - to support parallel conceptualization and representation of these different types of genetic variation that inform the discovery of G2P associations. We acknowledge that this is not a 'genotype' in the traditional sense, but this terminological choice highlights similarities that play out in parallel modeling of intrinsic and extrinsic genotype partonomies, and parallel syntactic formats for labeling instances of these genotypes. Our rationale here is that what we care about from perspective of G2P associations is identifying genomic features that impact phenotype - where experimental approaches include permanent introduction of intrinsic modifications to genomic sequence, and transient introduction of extrinsic factors that modify expression of specific genes. As the former is described by the traditional notion of a genotype, it seems a rational leap to consider the latter akin to an 'extrinsic genotype' wherein the alterations are externally applied rather than inherent to the genome. Finally, there is some precedent to thinking about such extrinsic modifications in terms of a genotype, in the EFO:0000513 ! genotype: "The total sum of the genetic information of an organism that is known and relevant to the experiment being performed, including chromosomal, plasmid, viral or other genetic material which has been introduced into the organism either prior to or during the experiment." genotype