Drosophila melanogaster OR The Fruit fly labs Genetics Drosophila melanogaster OR The Fruit fly labs

Why Use the Fruit fly Drosophila melanogaster is the classic laboratory organism for genetic study These small flies are called fruit flies, pomace flies, or vinegar flies. They are inexpensive, quickly reared in the lab ( life cycle in 10-14 days at room temperature but grow best at 25 C), have simple food requirements, take up little space and contain many mutant strains that are easily identified.

Charateristics Like all insects, Drosophila have 3 main body parts: head, thorax and abdomen. The major structures on the head are the large red (unless mutated) compound eyes. The thorax has six legs, and two wings

LIFE CYCLE Drosophila go through four stages in their lives, which take about 10-14 days to complete.

Stage 1: Egg Egg: eggs are laid by female on the food and take about 1 day to hatch.

Stage 2: Larval stage Larval stage: these are the maggots, which crawl through the food, eating as they go. This stage lasts about 7 days

Stage 3: Pupae Pupae: these are the cocoons in which the larvae metamorphose into adults. This stage lasts 5 days. During the last day the eyes and dark wings can be seen forming inside.

Stage 4: Adult Adults: Emerges from the pupal case white and elongated with wings still folded up. After about 1 hour the wings expand. After 8-10 hours the adults are sexually mature.

Fly Separation Flies have no morals!! If there is a male around, the female will become pregnant. Once a female has mated she stores enough sperm to fertilize all her eggs for life. To ensure controlled mating, it is important to use virgin female flies. Thus one must sex and separate the males from female flies and store them in separate vials.

Flynap To examine flies, they need to be immobilized or they will fly away. We will be using flynap to immobilize our flies. Place the flynap wand in the vial for about a minute, the flies will begin to fall asleep While flynap is safe for flies, over anesthetizing flies could be fatal. When done looking or sorting the flies, put the flies back in the vial, but not on fresh food. If the food is verywet or loose, the flies can drown.

Determining the sex of flies Color and shape of abdomen are not reliable for sexing newly emerged adults. Use the sex combs located on the front legs of the male to differentiate between male or female. Also remember that when first hatched, the female hatch before the males, so you may not have a 1: 1 male, female ratio

Sex combs of a male fly

Female Fly

Drosophilia Facts Drosophilia flies only have 4 chromosomes. During the course of this class, we will be performing: monohybrid crosses, dihybrid crosses and sex-linked crosses. A Monohybrid cross is a cross involving two parents, who differ in the expression of a single heritable trait. A dihybrid cross is a cross involving parents, who differ in the expression of two heritable traits. Monohybrid and Dihybrid crosses can be performed using genetic traits located on chromosomes 1,2, 4. Sex-linked crosses contain traits that are controlled by genes located on the sex chromosomes ( chromosome #3).

Wild Type (Normal Flies)

Apterous Flies (no wings)                                                                                              Contact FlyBaseversion FB2007_02, released September 12, 2007

Vestigial (wings reduced)

Bar eyed (narrow eyes)( sex-linked)

Sepia eyes ( eyes brown and change to black as fly ages)

White eyes

Curly wings