CULTURE OF DROSOPHILAAND ITS LIFE CYCLE
An Introduction to Drosophila melanogaster
Drosophila melanogaster is a small, common fly found near unripe and rotted
fruit. It has been in use for over a century to study genetics and behavior.
Thomas Hunt Morgan was the preeminent biologist studying Drosophila early in
the 1900’s. He was the first to discover sex-linkage and genetic recombination,
which placed the small fly in the forefront of genetic research. Due to its
small size, ease of culture and short generation time, geneticists have been
using Drosophila ever since.
Fruit
flies are easily obtained from the wild and many biological science companies
carry a variety of different mutations. In addition these companies sell any
equipment needed to culture the flies. Costs are relatively low and most
equipment can be used year after year. There are a variety of laboratory
exercises one could purchase, although the necessity to do so is questionable.
Why
use Drosophila?
Teachers should use fruit flies
for high school genetic studies for several reasons:
1. they are small and easily handled.
2. They can be easily anesthetized and manipulated individually with unsophisticated equipment.
3. They are sexually dimorphic (males and females are different), making it is quite easy to differentiate the sexes.
4. Virgins fruit flies are physically distinctive from mature adults, making it easy to obtain virgin males and females for genetic crosses.
5. Flies have a short generation time (10-12 days) and do well at room temperature.
6. The care and culture of fruit flies requires little equipment is low in cost and uses little space even for large cultures.
1. they are small and easily handled.
2. They can be easily anesthetized and manipulated individually with unsophisticated equipment.
3. They are sexually dimorphic (males and females are different), making it is quite easy to differentiate the sexes.
4. Virgins fruit flies are physically distinctive from mature adults, making it easy to obtain virgin males and females for genetic crosses.
5. Flies have a short generation time (10-12 days) and do well at room temperature.
6. The care and culture of fruit flies requires little equipment is low in cost and uses little space even for large cultures.
ClassificationDomain: EukaryotE
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Drosophilidae
Genus: Drosophila (“dew lover”)
Species: melanogaster (“dark gut”)
Life cycle of Drosophila melanogaster
Drosophila melanogaster exhibits complete metamorphism, meaning the life cycle includes an egg, larval (worm-like) form, pupa and finally emergence (eclosure) as a flying adult. This is the same as the well-known metamorphosis of butterflies. The larval stage has three instars, or molts.
 Day 1: Eggs hatch Day 2: First instar (one day in length) Day 3: Second instar (one day in length) Day 5: Third and final instar (two days in length) Day 7: Larvae begin roaming stage. Pupariation (pupal formation) occurs 120 hours after egg laying Day 11-12: Eclosion (adults emerge from the pupa case).
Females
become sexually mature 8-10 hours after eclosion
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The generation time of Drosophila melanogaster varies with temperature. The above cycle is for a
temperature of about 22°C (72°F). Flies raised at lower temperature
(to 18°C, or 64°F) will take about twice as long to develop.
• Females can lay up to 100 eggs/day.
• Virgin females are able to lay eggs; however they will be sterile and few in number.
• Females can lay up to 100 eggs/day.
• Virgin females are able to lay eggs; however they will be sterile and few in number.
After
the eggs hatch, small larvae should be visible in the growing medium. If your
media is white, look for the small black area (the mouth hooks) at the head of the
larvae. Some dried premixed media is blue to help identify larvae however this
is not a necessity and with a little patience and practice, larvae are easily
seen. In addition, as the larvae feed they disrupt the smooth surface of the
media and so by looking only at the surface one can tell if larvae are present.
However, it is always a good idea to double check using a stereo microscope.
After the third instars, larvae will begin to migrate up the culture vial in
order to pupate.
culture Media Preparation:
culture Media Preparation:
- Ø Weigh corn flour, D-Glucose, Sugar, Agar and yeast powder separately and keep them aside.
- Ø Take the required quantity of water based on the need (for example, for 6 litres of fly media, take 6 litres of water) in a pressure cooker.
- Ø Warm the water (approximate temperature 35⁰C) and add corn flour. Mix thoroughly to remove any clumps. Add other ingredients (D-Glucose, sugar, agar and yeast powder) and mix again.
- Ø Close the pressure cooker lid without cooker weight/whistle and keep on high heat for 5 minutes.
- Ø Open the pressure cooker and mix thoroughly
- Ø Close the pressure cooker with cooker weight/whistle and boil at 120 deg C for 25 minutes at low flame.
- Ø Once media is cooked, turn the heat off and wait to cool for 15-20 minutes.
- Ø Once the pressure is released (after ~15 minutes), open the cooker and mix thoroughly.
- Ø Cool the media to 50-55 deg C (make sure that it is checked with thermometer)
- Ø Add TEGO solution which has been mixed with alcohol, followed by propionic acid and ortho- phosphoric acid and mix thoroughly.
- Ø Tego-sept(Methyl parahydroxy benzoate) is mixed in Ethanol
- Ø Gajju’s media is liked by flies and they tend to be healthier and lay more eggs in the media. Hence, we ask Gajju to make his special media for our sickly fly stocks.
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