Organisms used to closely study and elucidate our understanding of basic biological phenomena that might not be easily researched in advanced organisms. In general, they possess characteristics such as small size, short life span and ease of cultivation.
The segment of DNA involved in producing a polypeptide chain. It includes regions preceding and following the coding region as well as intervening sequences (introns) between individual coding segments (exons). (Genes V, p.1242)