Genetic variations can span any level of granularity from a full genome or genotype to an individual gene or sequence alteration. These variations can be represented at the physical level (DNA/RNA macromolecules or their parts, as in the ChEBI ontology and Molecular Sequence Ontology) or at the abstract level (generically dependent continuant sequence features that are carried by these macromolecules, as in the Sequence Ontology and Genotype Ontology). The causal relations in this hierarchy can be used in linking either physical or abstract genetic variations to phenotypes or diseases they cause or contribute to. Environmental exposures include those imposed by natural environments, experimentally applied conditions, or clinical interventions.