Chado is a relational database schema that underlies many gmod installations. it is capable of representing many of the general classes of data frequently encountered in modern biology such as sequence, sequence comparisons, phenotypes, genotypes, ontologies, publications, and phylogeny. it has been designed to handle complex representations of biological knowledge and should be considered one of the most sophisticated relational schemas currently available in molecular biology. the price of this capability is that the new user must spend some time becoming familiar with its fundamentals.