OPOSSUMS ARE MARSUPIALS. If you open just about any field guide to North American mammals, the opossum will probably be the very first of the 380 or so mammal species described. That's because opossums are our only marsupial, and marsupials are considered very ancient forms of mammals.
operator - an agent that operates some apparatus or machine; the operator of the switchboard. manipulator. causal agency, causal agent, cause - any entity that produces an effect or is responsible for events or results. company operator - an operator who works for a company. driver - the operator of a motor vehicle.
(1) (genetics) A segment of DNA where the repressor binds to, thereby preventing the transcription of certain genes. (2) (surgery) The one performing surgical procedures. (Genetics) In the Operon Model, the operator is the gene in which a repressor binds. This results in the prevention of the RNA polymerase from binding to it, thus, preventing the expression of certain genes in the operon unit. Word origin: Latin operÄ ( rÄ« ) (to work, effect).