How the Humble Fruit Fly Changed Science

This is a picture of Veronica Rodrigues, a biologist. The photograph was taken around 1979 when she was a PhD student at the Tata Institute of Fundamental Research (TIFR) in Bombay, India. Wondering what she’s looking at so intently?

Well, fruit flies.

Drosophila has been used in research since the early 20th century. In this story, we look at fruit flies and their fascinating journey over the years, across countries, generations, and cultures.

Castle’s decision greatly influenced Thomas Hunt Morgan, an evolutionary biologist and geneticist whose work on inheritance (around 1910) helped put the fruit fly on the map as a model organism.

Most images of Drosophila will show you that it has bright red eyes. What Morgan noticed, however, was a male fruit fly with pale white-ish eyes. These eyes were the result of a random mutation of a gene, a fairly common occurrence.

Morgan was able to identify that the gene with the random mutation was located in the flies’ sex chromosomes (think X and Y). This was a groundbreaking discovery because up until then, no one really knew where our genes were. Connecting these dots would prove to be the foundation of modern genetics.

Muller’s discovery sent shockwaves through the scientific community. His work connecting radiation and mutations connected physics and biology, two subjects that had not mingled much until this point. This acted as a trigger that eventually led to many physicists shifting over to biology.

What Benzer really liked about fruit flies was their small size, short life span and statistically large populations. His lab studied the flies’ circadian rhythms and observed the effects of genetic mutations on behaviour. One particular mutation they studied was called, "drop-dead," because it caused perfectly healthy flies to suddenly, well, you know, drop dead.

Incidentally, there is also the "Kumbhakarna" gene that causes flies to take forever to snap out of induced-paralysis, as well as the “cheap date” gene that increases a fruit fly’s susceptibility to alcohol. But the topper must be the “I’m Not Dead Yet” gene that increases the longevity of flies. Who would’ve guessed that geneticists had a thing for Monty Python references?

"When I was at MIT, there was a man, a Japanese scientist, David Suzuki. He came to MIT to give a lecture. David Suzuki had discovered the first temperature-paralyzed mutants of Drosophila. So I read David Suzuki's papers and David came to give a lecture at MIT and I remember that he had a test tube of Drosophila mutant paraTS, it is called paralyzed temperature sensitive, in his coat pocket. When he was lecturing, he took out the tube and held it in his hand and when he removed the hand, of course, all the flies were paralyzed and fell to the bottom. I was fascinated by this lecture, because anybody could see that this paralysis might involve the blocking of the nervous system. So I actually made up my mind right then that that was what I was going to work on-- to look at paralyzed mutants."

Olfaction was a mainstay for Siddiqi and for TIFR's Molecular Biology Unit. This image shows Siddiqi's attempt (much later, in 1991) to improve upon a fly maze.

Which brings us back to that image of Veronica Rodrigues and her fruit fly maze.

In the mid-1970s, the Kenya-born Rodrigues applied to TIFR to do a PhD under Obaid Siddiqi thinking he still worked on bacteria, as shown in this letter. She then decided to research olfaction in the fly, even building her own instrument – the Y-maze shown beside her in the previous photo.

What they found was that similar genes exist in more complex organisms. This was a stepping stone to eventually discovering that humans share versions of many genes with Drosophila. According to a 2001 study, it’s a 70% match.

But no one knew this when Drosophila first entered research. For Castle, they were an easier alternative to guinea pigs and mice. Morgan picked Drosophila because it was an organism whose genes had already been studied to some extent. Benzer says he chose Drosophila because it was convenient. Siddiqi picked up from Benzer’s suggestion and, along with Rodrigues, pioneered a new field in Drosophila research.

Jacques Monod, a French biochemist, famously said that “anything found to be true of E. coli must also be true of elephants.” This implies that the simplest of model organisms can help us understand the most complex creatures. But is this always the case?

As Sanjay Sane, a former student at TIFR, and now a scientist at NCBS, says here, using model organisms comes with a limitation. Despite the tools and knowledge at your disposal, there is always the possibility that the organism you are studying is not suited to the question you are pursuing.

Drosophila is a model organism and a tool of understanding. But beyond the literal meaning in biology, it has also been a model in other ways. It connects stories. Stories of education, research, science and community. The fruit fly has propelled itself on an interlinking journey across many disciplines, countries, and people. It is the link between these stories that gives us new ways of seeing