Model Organisms

This tiny fly ( Drosophila melanogaster ), about three millimeters long, has been used to study classic genetics and mutations since the early twentieth century. It’s still one of the most important and widely used model organisms for genetics and developmental biology. It has a short life cycle, it’s cheap to buy, easy to raise and handle, and its genome has been completely mapped and sequenced. Fruit fly researchers have a tradition of using whimsical names to describe genetic mutations. For instance, "leonardo" and "dunce" describe two gene variations that affect a fly’s ability to learn new odor tasks. The genes involved in learning in flies are very basic to brain function; humans have similar genes that operate at a cellular level in our brain.

On the fruit fly as a model organism for studying the genetics of memory:
"When we first started working on learning and memory in Drosophila, we did so primarily because it was the only model animal that we could do genetic experiments with. It was the only genetic model system that allowed us to make mutants and map genes. There were other genetic model systems–nematodes, yeast, and bacteria–but these don’t show associative learning. The fruit fly was the only one."

— Tim Tully , Research biologist, Cold Spring Harbor Laboratory

On why economics is sometimes important in choosing a model organism:
"I persist in this model system because of the economy of scale. There are fewer genes in the fly than in a mouse, so it’s simpler at the genetic level, and there are fewer neurons in the fly’s brain than in a mouse’s brain, so it’s simple at the level of circuitry. And I think that those two levels of simplicity make the problem of trying to understand how genes influence memory a little bit more tractable in my time.

"And the economy of scale applies to the cost in time and resources to do genetics. Flies have a two-week generation cycle, and we can raise thousands for pennies. Mice have a four-month generation cycle, and it costs fifty cents a day per mouse to house them."

— Tim Tully , Research biologist, Cold Spring Harbor Laboratory

On the differences between flies and humans:
"One of the primary differences between a fruit fly and a human is in the complexity of the circuitry. So the analogy here is the fly is like a transistor radio and a human is like a personal computer. They’re both built of transistors and resistors, and small wires connecting them, which are the genes involved in memory formation. But, clearly, the wiring diagram, the circuitry of a PC is much more complex than the circuitry of a transistor radio. So finding the genes involved is part of the answer, and the discovery for human memory formation at the level of genes. But the discovery of the circuitry will require species closely related to humans."

— Tim Tully , Research biologist, Cold Spring Harbor Laboratory

To learn more about Drosophila :
Flybase is a comprehensive database about genetics and molecular biology of Drosophila .

Purdue University's Interactive Fly provides some developmental information about Drosophila, as well as a genetic reference.

Try our online comparison of fruit flies and see how mutations can alter their color and shape!