Why use the fly in research?

WHY USE THE FLY IN RESEARCH ?

The fruit fly (Drosophila melanogaster) is one of the most well understood of all the model organisms.

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

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.

You know those annoying little bugs that like to get in your fruit if you leave it on the counter? Well they're called Drosophila melanogaster (or just fruit flies) and they've been used to study genetics for over 100 years. This interactive website is designed to introduce biology students to research on model organisms while reviewing genetics basics.

Learning about Genetics Using Flies

Model organisms are species that are studied to understand the biology of other organisms, often humans. Fruit flies share 75% of the genes that cause disease with humans, so scientists can learn about human genetics by studying fruit fly genetics. It is not only the flies themselves that the scientists are interested in, but also understanding the basic biology that all organisms have in common. There are hundreds of labs across the country who are entirely dedicated to studying fruit flies, including ten here at UNC.

Low Maintenance Creatures

Fruit flies are great to work with in a research setting because they are relatively easy to take care of, especially compared to larger and more expensive organisms like rats or fish. They are also small (only a few millimeters long) but not so small that they can't be seen without a microscope. This allows for scientist to keep up to millions of them at one time. In a fruit fly lab, there are stacks and stacks of fruit flies living in little vials (see picture to the right). The only care they need is to have their food changed every ten to fourteen days by transferring them into new vials. They eat a pastey substance, called media, that goes in the bottom of the vial and contains all the water they need soaked into it. The vials can be kept at room temperature, however incubators are used to expedite or slow the life cycle as needed. Basically they're easy to work with, adorable, and don't ask for much: these models are no divas.

Knocking Them Out

The fruit flies do fly, of course, so they have to be knocked out before they come out of their vials. When a scientist needs to take a look at the fruit flies under the microscope they can be easily anesthetized. The options for anesthetizing the flies include drugging or cooling them, however, most labs choose to gas them with carbon dioxide. There are carbon dioxide lines that run across the work benches that the scientists can hook up to vials of flies. A little carbon dioxide puts them to sleep long enough to look at them under the microscope but within a few minutes they're back to normal without any side effects. Well, they might be a little dizzy after, but they don't complain much.