Why fruit flies, mice and baker's yeast keep showing up in labs
A fly that breeds in days, a bacterium from the human gut and a humble weed called Arabidopsis have taught biology more than almost any other creatures. Because all life shares ancestry, what works inside a fruit fly often works inside a person, and that shared machinery lets researchers test ideas that would be impossible in humans.
A model organism is a non-human species studied intensively in the hope that its lessons apply to others. The approach works because evolution has conserved genes and metabolic pathways across very different creatures. Favourites span all domains of life plus viruses: the gut bacterium Escherichia coli, one of the first tools of molecular biology, along with baker's yeast, the T4 virus that infects bacteria, the fruit fly Drosophila melanogaster, the house mouse and guinea pigs. Species with short generation times, such as fruit flies and nematode worms, suit genetic work.
Some milestones came straight from such studies. Between 1910 and 1927 Thomas Hunt Morgan's fruit flies showed that chromosomes carry genes, and Eric Kandel credited that work with turning biology into an experimental science. Around the same time William Ernest Castle, working with Abbie Lathrop, bred the DBA mouse, the start of systematic inbred strains. Much earlier, Antoine Lavoisier put a guinea pig in a calorimeter to show that breathing is a form of combustion.
Medicine drew heavily on the method. Emil von Behring demonstrated diphtheria toxin in guinea pigs and developed an antitoxin, and the 1925 serum run to Nome that delivered it is remembered in the Iditarod sled race. Frederick Banting's experiments with dogs led, with John Macleod, to the discovery of insulin in 1922. John Cade found in guinea pigs the calming effects of lithium salts, which transformed care for bipolar disorder.
Polio vaccines depended on rhesus monkeys. Jonas Salk's vaccine, released in 1955, cut American polio cases fifteenfold in five years, and Albert Sabin's version, mass-produced from 1963, had nearly eliminated the disease in the United States by 1965. Producing them is estimated to have used some 100,000 monkeys, each yielding about 65 doses. Researchers classify disease models by closeness: homologous ones share causes and symptoms with the human illness, while predictive ones match only a few features.
Source: Model organism
