Fruit fly: The tiny star behind five Nobel Prizes in medicine

“I am very pleased for the fruit fly,” was Michael Rosbash’s reaction to the news of his having shared the 2017 Nobel Prize in medicine with two others. The trio got the award for their work on the body clock — circadian rhythm.

Rosbash has reason to be pleased. Since the time when Thomas Hunt Morgan, a professor of Zoology at Columbia University started breeding fruit flies in his laboratory in a bid to understand the then elusive transmitter of hereditary information — the gene — better, the fruit fly (Drosophila melanogaster) has been the means of unearthing copious amounts of information about the gene, its structure, nature, function and its role in various diseases. The road was strewn with Nobels; Morgan got one in 1933.

A look at the spectacular “career” of Drosophila in genetics, the tiny insect that has pages dedicated to it on the websites of some of the most prestigious universities and research institutes of the world.

How did it all start?

At a time when the world was still discovering Gregor Johann Mendel, the 19th century Austrian monk who, long after his death came to be regarded as the father of genetics, Morgan, a cell biologist, incredulous at first of Mendel’s contention that hereditary information is transmitted through units, began his quest for more information about these units. He started breeding maggots sometime around 1905.

“Bunches of overripe bananas hung from sticks. The smell of fermented fruit was overpowering, and a haze of escaped flies lifted off the tables like a buzzing veil every time Morgan moved. The students called his laboratory the Fly Room. It was about the same size and shape at Mendel’s garden — and in time it would become an equally iconic site in the history of genetics,” writes Pullitzer winning author Siddhartha Mukherjee in The Gene. (Mukherjee himself is an assistant professor at Columbia and a staff cancer physician at the Columbia University Medical Centre.) It was in this room that Morgan first discovered a red-eyed fly among a swarm with white eyes and identified mutation or spontaneous genetic changes in animals. It had already been identified in plants. The Fly Room was the predecessor to many such across the world for years to come as Drosophila maintained its star status in genetics despite prodigious evolution of knowledge about genes.

Morgan went on to win the Nobel Prize “for his discoveries concerning the role played by the chromosome in heredity”.

Why has Drosophila remained the preferred choice of geneticists for more than a century?

There are several reasons, but the most important one perhaps is the fact that the fruit fly genome has just 8 chromosomes (four pairs) — humans have 46. Hence the fruit fly genome is easier to map and understand even if the behaviour and nature of individual genes remain unaffected by the size of the genome. What works for the fruit fly is that an astounding 60% of its genes are found in humans in a similar form. According to the Max Planck Society a research organisation based in Germany, “Around 75 per cent of the genes which are known to cause illnesses in humans, also occur in flies. Drosophila possesses more than 90 per cent of the genes that can trigger cancer in humans.”

It is also a prolific breeder; it is very easy to raise generations of flies in a small box within a very short time, speed that is crucial in chronicling the course of heredity and extrapolating that information into an understanding of genes. As study of genes advanced to a phase when scientists began tinkering with it to make better or disease free organisms (eugenics), it was found that it is also easy to modify the fruit fly genome to study how genotype (gene type) alters phenotype (outward appearances). Thus continued Drosophila’s association with genetics.

How many “fly scientists” have won the Nobel since Morgan?

Among Morgan’s students who had worked in the Fly Room with him was Herman Muller, who won the Nobel Prize for his discovery that the fruit fly gene could be altered by radiation. Muller incidentally had travelled to Germany during the Third Reich in the belief that Berlin would be the seat of a new revolution in the emerging science of genetics and had watched up close Hitler’s experiments with Eugenics or betterment of the human race. George Beadle, who along with Edward Tatum won the 1958 Nobel Prize in physiology and Medicine “for their discovery that genes act by regulating definite chemical events” was also Morgan’s student in the Fly Room, In 1995 three development biologists — Edward B Lewis, Christiane Nusslein-Volhard and Eric F Wieschaus — won the award for discovering the role of key genes in the development of the fruit fly embryo that also play a crucial role in human embryonic development.

The 2017 prize is further proof of how the Drosophila juggernaut rolls on in the world of genetics

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