Drosophila Research and our Basic Understanding of Genetics

Drosophila melanogaster, more commonly known as the fruit fly due to its common proximity to unripe or dying fruit, is commonplace in genetics courses and university labs around the globe. This small and prolific species has been a staple of genetics research for more than a century, giving researchers the means to understand some of the basics of human genetics and develop means to study more complex genomes.

Why the Fruit Fly?

Drosophila were, and still are, used by researchers and educators for a number of reasons:

-They are small and easily maintained and handled.

-They breed prolifically with a short life cycle, reducing the amount of time between generations for experiments and observations requiring several.

-Each female lays enough eggs to make statistical analyses among the same set of offspring in the same generation feasible.

-They are relatively cost-efficient.

– The genome is relatively simple and mutations can be targeted to specific genes.

In recent years, the structure of the Drosophila chromosome and its embryonic development outside the body has maintained this species’ attractiveness as a current model in research, keeping the fly from being just a teaching tool.

Early Studies of Mendelian Genetics and Heredity

Mendelian genetics, the simple understanding of how heredity works, was the brainchild of a Central European monk working with pea plants. Gregor Mendel’s observations were published in 1866, but as described by Dennis O’Neil of Palomar College in California, the scientific community did not take notice until 1900. Thomas Hunt Morgan, who received a Nobel Prize in 1933 for his fruit fly work, began working with Drosophila in the early 1900s in response to the many questions remaining about heredity.

1995 Nobel Laureate Edward B. Lewis credits Morgan with establishing the basis for lab-rearing fruit flies, including the use of equipment and standardized breeding conditions. In 1910, Morgan discovered the first fruit fly mutation – white eyes. Using this mutation as a focal point, sex-linked inheritance was discovered. Morgan established the famous “fly room” at Columbia University, which led to many discoveries, including a second mutation in 1911 – rudimentary wings, which is also sex-linked. Using this mutation as a focal point led to the discovery of crossing over, also known as recombination.

One of Morgan’s students was the first to perform genetic mapping on the basis that genes occur in a linear arrangement. The lab’s combined work led to the understanding that chromosomes, which were discovered by Walther Flemming a few decades earlier, contain the hereditary units discovered by Mendel . Thus, Morgan and his early fruit fly work laid the basis for modern genetic theory, though it would be decades before DNA itself was discovered.

Drosophila’s Contribution to Understanding the Genome

The genome is made up of genes, the name given the hereditary units discovered by Mendel and Morgan. Manipulating the genetic material in this species via breeding and/or gene targeting has allowed researchers to identify the function of specific genes, the consequences of particular mutations, and to develop methods for gene transfer. Rubin and Lewis outlined the most notable contributions of fruit flies in the journal Science in 2000.

Fruit flies have contributed to the understanding of ionizing radiation as a cause of genetic damage, types of genetic damage that can be incurred, and the consequences of such damage. In addition, the method of whole-genome scanning was developed, which is useful to understanding the phenotypic consequences of genotypic changes (i.e. mutations). DNA cloning was also first done using fruit flies – the technique is now a staple in molecular biology labs and medical research for a number of research methods. Techniques in sequencing and identifying genes and loci involved in disease were also developed using the drosophila genome, without which much of what is currently understood about elements of the human genome, hereditary disease, and cancer would not be known.

The entire Drosophila genome sequence was published in the March 24, 2000 issue of Science, but work continues as a database of variants and identified genes is maintained as a joint project of universities and government agencies (FlyBase).