Model organism

A model organism is an organism used to investigate biological processes through accessible, repeatable experiments. Its value combines experimental tractability with a carefully delimited relationship to other organisms. For example, a gene deletion in Saccharomyces cerevisiae can test whether a gene is required for growth under specified conditions; adding another gene can test functional complementation. Such interventions support causal inference more directly than merely noticing that a gene and a phenotype occur together. ^[ref]

The striking opportunity is to ask two experimentally separate questions: what does this component do here, and which part of that function survives a change of species or conditions? The yeast cross-species complementation experiment makes both questions concrete. Model organism evidence transfer requires specifying the function being compared; a useful model organism need not reproduce every feature of another organism.