Student writer: Sarah Robbins
Student editors: Rita Chakrabarti,
23andMe editor: Becca Krock, Thao Do
Animal models help scientists to figure out how cells, genes, organs, and physiological pathways work in order to better understand these same processes in other species, including us. New discoveries in medicine often rely on trials in animals before they are tested in humans.
What animal are we talking about today?
The fruit fly, scientifically known as Drosophila melanogaster.
A fruit fly? Really?
Yes, really! Despite our many differences, fruit flies share many similarities with humans. Fruit flies, like humans, are animals, so our cells are very similar in structure. For example, fruit fly cells have a cell membrane, but no cell wall — which is different in plants, which have a cell wall. Flies have eyes, brains, and muscles, even if they are a little different than ours, which makes them useful model organisms.
Tell me more about the fruit fly genome.
Fruit flies have approximately 14,000 genes across 168 million base pairs of DNA.
But how does this help scientists learn about human genetics?
Flies and humans share about two-thirds of disease-causing genes, meaning we can study these shared genes in fruit flies [1]. Because of these genetic similarities, Drosophila are used as models to study diseases like Parkinson’s, Huntington’s, and cancer. Discoveries made using model organisms can lead to valuable insights about diseases and potential targets for developing new treatments.
Who decided to start studying fruit flies?
Thomas Hunt Morgan, an evolutionary biologist, is largely credited with establishing the fruit fly as a model for genetic studies. His flies studies began in 1907, later leading to the foundation of his “Fly Room” at Columbia University [2]. Dr. Morgan discovered that some traits only affect males, as a result of the differences in chromosomes between male and female flies. This holds true in humans as well, and it is now known that there are sex-linked diseases, such as color blindness. These studies, along with his work on the role of the chromosome in inheritance, won Morgan the Nobel Prize in Physiology or Medicine in 1933 [3].
How did studying fruit flies win Thomas Hunt Morgan the Nobel Prize?
Dr. Morgan bred many fruit flies, looking for any offspring that had unusual characteristics, such an uncommon wing shape or eye color [4]. One day, Morgan noticed a fly with white eyes, which was very different from the normal red color of fruit fly eyes. He did experiments breeding many other flies and found that white eye was a trait only inherited by male flies [5]. This was the way he made the connection between sex characteristics and other traits.
Why study fruit flies instead of something else?
Drosophila are great model organisms because they are small, and thousands can be kept in a tiny laboratory space. Fruit flies are also inexpensive to feed and house, which can leave a researcher more money for other lab supplies. Drosophila are more similar to humans than some other common model organisms – yeast or worms – which makes them useful for studying diseases that affect humans. Also, flies only have four chromosomes, which makes figuring out how genes are arranged a bit easier. Flies are also especially useful for working out complicated pathways or interactions since you can generate lots of flies in a small amount of time. They also grow and mature quickly, making it easy to breed many flies and complete many experiments more quickly than in larger animals. Their entire life cycle is only about one to two months, so their development is easily observed in the lab [6].
Who uses flies for research today?
Many researchers still use flies for genetic studies. Kathleen Cunningham, a fifth-year PhD student at Johns Hopkins School of Medicine working in the lab of Tom Lloyd, uses fruit flies as a model to study amyotrophic lateral sclerosis, or ALS.
To dive further into this research, I spoke with Kathleen about her work in the lab with her tiny laboratory assistants.
SR: Can you tell us about more about ALS?
KC: “ALS, also known as Lou Gehrig’s disease, affects neurons in the brain that control movement. When the neurons that control our muscles lose their connections to other cells around them, they start to die. The disease usually affects people in their 50s and 60s and progresses rapidly within 3-5 years.”
SR: How do you spend your days in the lab?
Kathleen spends most of her time in the fly room, at the microscope taking cool images, and working out the pathways involved in ALS. Kathleen estimates that only about 10% of the gene variations that contribute to ALS are already known. Eventually, Kathleen and her colleagues in Dr. Lloyd’s lab hope to use fruit flies to contribute to personalized medicine approaches to ALS treatment.
SR: What’s your favorite thing about your work?
KC: “There isn’t as much translational [or disease-oriented] work in flies, so studying disease in flies is more unique. [I found it] compelling to study a disease but I’m very interested in the mechanisms of basic biology. When they converge, you can make a breakthrough. It’s a balance between patient care and increasing our understanding.”
Thanks for your help, Kathleen! Good luck in your studies!
And don’t forget – the fruit fly is just one of many tiny laboratory assistants!
- NHGRI. “Background on comparative genome analysis.” 12/2002. https://www.genome.gov/10005835/background-on-comparative-genomic-analysis/.
- Genome News Network. “Genetics and Genomics Timeline: 1910.” 2004. http://www.genomenewsnetwork.org/resources/timeline/1910_Morgan.php.
- Miko I. “Thomas Hunt Morgan and Sex Linkage.” 2008. https://www.nature.com/scitable/topicpage/thomas-hunt-morgan-and-sex-linkage-452.
- Kandel ER. “Thomas Hunt Morgan at Columbia University.” http://www.columbia.edu/cu/alumni/Magazine/Legacies/Morgan/.
- Morgan TH. (1910.) “Sex limited inheritance in Drosophila.” Science. 32(812):120-122. https://www.ncbi.nlm.nih.gov/pubmed/17759620. [Available at http://www.jstor.org/stable/pdf/1635471.pdf]
- Yourgenome. “Why use the fly in research?”. 6/9/2015. https://www.yourgenome.org/facts/why-use-the-fly-in-research.