Survey of Genomes - Drosophila melanogaster

In this episode from the survey of genomes, Kaitlyn Morse from the 2019 Hiram College Genetics course moves us into the world of eukaryotic genomes. Her focus is on the first model animal for genetic analysis - Drosophila melanogaster or as most people know it, the fruit fly.

Hello, and welcome back to genomics revolution. I am Kaitlyn Morse a guest scientist here today to talk about the organism Drosophila melanogaster, or what we know as the fruit fly. We may think of this insect as a pest but, it has been one of the most useful organisms in a biology/ genetics lab to date. You may be asking how is that possible? A small fly? Let’s discuss why Drosophila has become so important.

The discovery of Drosophila occurs in 1830 but, the first time Drosophila became a popular organism to study was back in 1910 in Thomas Hunt Morgan’s lab. He noticed that a male fly had white-eyes instead of the-wild-type eyes which were red. This lead to years of studying this organism and finding that eye type was found in the sex chromosome and was being passed on. The study of Morgan’s lab Lead to a deeper interest in Drosophila (5).
In the year of 1999, the entire genome of Drosophila was made available to researchers all over the world. They had concluded that the genome is approximately 180 Mb in size (6). The number of proteins found in drosophila was 30,493. The work of these scientists also solidified there are only four chromosomes in Drosophila (2). The first is a sex chromosome ( X chromosome) and the remaining three are autosome. Chromosome two and three are separated into left and right arms ( 2L, 2R, 3L, and 3R) (3). The fourth is a very small autosome. The first physical maps of the chromosomes was actually created in 1910 when the first lab found that the color of eyes was found in the sex chromosome (1). This was Thomas Hunt Morgan’s lab who discovered this as well. We can thank Morgan for the wide historical importance of Drosophila and the large group of scientists that were studying this organism for years after he did.

Why is Drosophila considered a model organism? Why is it so important to biology/ genetics ? First, after working with Drosophila for years and sequencing the genome they realized Drosophila is inexpensive, has a short lifespan, and has a reasonably small genome. The fly only takes 9-10 days to go from a fertilized egg to an adult. This makes it easy for scientists to create many new generations quickly and also study their genome because it isn’t too large in size. Next, Drosophila is know for having Transposons in their genome. As some of us may know, a transposons is a chromosomal segment that can move anywhere in the genome. This movement can cause a mutation, alter genome size, or duplicate the genetic material found in the cell. After the transposons in Drosophila were discovered, they determined they were helping maintain telomere lengths in Drosophila. The transposons are now being used biologically. Laboratories are now using Transposons for mutagenesis ( or causing genetic mutations) and transformations (4). But in my opinion the most important part of the research that has been done on this organism is how their genome is like the human genome. 75% of the genes responsible for human disease are highly conserved in this species. This allows for the study of human disease and for scientists to understand the disease outside of a human patient. In the study “The systematic analysis of Human Disease- Associated Gene Sequences in Drosophila melanogaster 548 drosophila genes were related to the human disease genes. 153 of these are associated with a known mutant allele and 56 others are marked by a P-element insertion in or near the gene (which is a transposons that is more likely to move here) . Knowing humans and drosophila had highly conserved genes allowed for this study to be made possible. The scientists used drosophila to study human metabolic disease. The genes and pathways are the same in the insect as humans which allows for manipulation of these pathways. Scientists have now been able to use this manipulation to cause a fly to be diabetic or even show an obese phenotype. Using Drosophila to study diseases has now led scientists to believe they can create therapeutic ways to treat these diseases by looking at how it affects drosophila first (7).

This organism can lead to many different therapeutic remedies and better understandings of diseases. Using Drosophila to better understand how things work in humans can lead to faster treatments for people. While many people just believe that the fruit fly is just a pest around their house, hopefully now you may have a better understanding how useful this organism is. It is important to continue to study this organism in order to continue to make strides in genetics to help lead to better medical treatment . I hope this podcast was both informational and interesting. Thanks for listening to Genomics Revolution. Kaitlyn Morse Signing off.

References:
1. Fruit flies in the laboratory. (2018, April 04). Retrieved from
https://www.yourgenome.org/stories/fruit-flies-in-the-laboratory
2. Drosophila melanogaster (ID 47). (2015). Retrieved from https://www.ncbi.nlm.nih.gov/genome/?term=drosophila melanogaster.
3. Hales, K. G., Korey, C. A., Larracuente, A. M., & Roberts, D. M. (2015, November). Genetics on the Fly: A Primer on the Drosophila Model System. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4649653/#!po=12.3762
4. Cheng, L., Baonza, A., & Grifoni, D. (2018, August 30). Drosophila Models of Human Disease. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6136514/
5. Thomas Hunt Morgan and Sex Linkage. (n.d.). Retrieved from
https://www.nature.com/scitable/topicpage/thomas-hunt-morgan-and-sex-linkage-452
6. Adams, M. D. (2004, February 20). The Genome Sequence of Drosophila melanogaster. Retrieved from
http://science.sciencemag.org/content/287/5461/2185?casa_token=oSaTWt9OxqIAAAAA:Pzd5 plb0P9n9IEF1oU8EZkw17VL9n3_JY3XQT9DO7-Vb6DKhILded0YuqOv-H11U7-0lcBPmpg1kXw
7. Reiter, L. T. (2001). A Systematic Analysis of Human Disease-Associated Gene Sequences In Drosophila melanogaster. Retrieved from https://genome.cshlp.org/content/11/6/1114.full.pdf