Why use the fly in research?

Key facts

• The fruit fly (Drosophila melanogaster, ‘Drosophila’ hereafter) is the most extensively used and one of the most well understood of all the model organisms.
• Drosophila fruit flies measure approximately 3 mm in length.
• Drosophila larvae are small, white and glossy with a similar appearance to worms. Within 5-6 days they increase around 1000-fold in weight.
• Adults in the wild are tan with black stripes on the back of the abdomen and vivid red eyes. However, there are many visible genetic mutations, including many different eye colours, which are valuable for geneticists studying Drosophila.
• Females live for about one month at room temperature but this can increase to over two months at lower temperatures.
• A female may lay 30-50 eggs per day throughout her lifetime at room temperature. Daily egg production is reduced at lower temperatures.
• The Drosophila feeds” and breeds on fermenting fruit or on other sources of fermenting sugar such as waste in drains or rubbish bins.
• The story of Drosophila in biological research began in the early years of the 20th century.
• Drosophila are ideal for the study of genetics and development.
• The complete genome sequence of the Drosophila was published in 2000.
• Its genome is 168,736,537 base pairs in length and contains 13,937 protein-coding genes (Ensembl).

A male red-eyed fruit fly
Image credit: Shutterstock

Benefits of the fruit fly

• The relationship between fruit fly and human genes is so close that often the sequences of newly discovered human genes, including disease genes, can be matched with equivalent genes in the fly.
• 75 per cent of the genes that cause disease in humans are also found in the fruit fly.
• Drosophila have a short, simple reproduction cycle. It is normally about 8-14 days, depending on the environmental temperature. This means that several generations can be observed in a matter of months.
• Fruit fly are small (3 mm long) but not so small that they can’t be seen without a microscope. This allows scientists to keep millions of them in the laboratory at a time.
• They are inexpensive to maintain in the laboratory.
• They require a simple diet consisting of simple sources of carbohydrates (cornmeal) and proteins (yeast extract).
• The only care they need is having their food changed regularly (every 10-14 days at 25˚C or 5-6 weeks at 18˚C).
• Drosophila have ‘polytene’ chromosomes, which means that they are oversized and have barcode-like banding patterns of light and dark. During early Drosophila research scientists could therefore easily identify chromosomal rearrangements and deletions under the microscope.
• It is relatively straightforward to mutate (disrupt or alter) fruit fly genes.
• The fruit fly provides a simple means of creating transgenic animals that express certain proteins, such as the green fluorescent protein of jellyfish.
• The long and distinguished history of research devoted to the study of the fruit fly means that a remarkable amount is now known about its biology.