GeneticsGeneticsDrosophila melanogasterDrosophila melanogaster

OROR

The Fruit fly labs The Fruit fly labs

Why Use the Fruit flyWhy Use the Fruit fly

DrosophilaDrosophila melanogastermelanogaster is the classic is the classic laboratory organism for genetic studylaboratory organism for genetic study

These small flies are called These small flies are called fruit fliesfruit flies, pomace , pomace flies, or vinegar flies.flies, or vinegar flies.

They are inexpensive, quickly reared in the lab They are inexpensive, quickly reared in the lab ( life cycle in 10-14 days at room temperature ( life cycle in 10-14 days at room temperature but grow best at 25 C), have simple food but grow best at 25 C), have simple food requirements, take up little space and contain requirements, take up little space and contain many mutant strains that are easily identified. many mutant strains that are easily identified.

CharateristicsCharateristics

Like all insects, Like all insects, Drosophila have 3 main Drosophila have 3 main body parts: head, thorax body parts: head, thorax and abdomen.and abdomen.

The major structures on The major structures on the head are the large red the head are the large red (unless mutated) (unless mutated) compound eyes.compound eyes.

The thorax has six legs, The thorax has six legs, and two wingsand two wings

LIFE LIFE CYCLECYCLE

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

Stage 1: EggStage 1: Egg

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

Stage 2: Larval stageStage 2: Larval stage

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

Stage 3: PupaeStage 3: Pupae

Pupae:Pupae: these are these are the cocoons in the cocoons in which the larvae which the larvae metamorphose into metamorphose into adults. This stage adults. This stage lasts 5 days. lasts 5 days.

During the last day During the last day the eyes and dark the eyes and dark wings can be seen wings can be seen forming inside.forming inside.

Stage 4: AdultStage 4: Adult

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

Fly SeparationFly Separation

Flies have no morals!! If there is a male Flies have no morals!! If there is a male around, the female will become pregnant.around, the female will become pregnant.

Once a female has mated she stores Once a female has mated she stores enough sperm to fertilize all her eggs for enough sperm to fertilize all her eggs for life.life.

To ensure controlled mating, it is important To ensure controlled mating, it is important to use virgin female flies. Thus one must to use virgin female flies. Thus one must sex and separate the males from female sex and separate the males from female flies and store them in separate vials.flies and store them in separate vials.

FlynapFlynap

To examine flies, they need to be immobilized or To examine flies, they need to be immobilized or they will fly away.they will fly away.

We will be using flynap to immobilize our flies.We will be using flynap to immobilize our flies. Place the flynap wand in the vial for about a Place the flynap wand in the vial for about a

minute, the flies will begin to fall asleepminute, the flies will begin to fall asleep While flynap is safe for flies, over anesthetizing While flynap is safe for flies, over anesthetizing

flies could be fatal. flies could be fatal. When done looking or sorting the flies, put the When done looking or sorting the flies, put the

flies back in the vial, but not on fresh food. If the flies back in the vial, but not on fresh food. If the food is verywet or loose, the flies can drown.food is verywet or loose, the flies can drown.

Determining the sex of fliesDetermining the sex of flies

Color and shape of abdomen are not Color and shape of abdomen are not reliable for sexing newly emerged adults.reliable for sexing newly emerged adults.

Use the sex combs located on the front Use the sex combs located on the front legs of the male to differentiate between legs of the male to differentiate between male or female.male or female.

Also remember that when first hatched, Also remember that when first hatched, the female hatch before the males, so you the female hatch before the males, so you may not have a 1: 1 male, female ratio may not have a 1: 1 male, female ratio

Sex combs of a male flySex combs of a male fly

Female FlyFemale Fly

Drosophilia FactsDrosophilia Facts Drosophilia flies only have 4 chromosomes.Drosophilia flies only have 4 chromosomes. During the course of this class, we will be performing: During the course of this class, we will be performing:

monohybrid crosses, dihybrid crosses and sex-linked monohybrid crosses, dihybrid crosses and sex-linked crosses.crosses.

A A Monohybrid crossMonohybrid cross is a cross involving two parents, is a cross involving two parents, who differ in the expression of a single heritable trait.who differ in the expression of a single heritable trait.

A A dihybrid crossdihybrid cross is a cross involving parents, who is a cross involving parents, who differ in the expression of two heritable traits.differ in the expression of two heritable traits.

Monohybrid and Dihybrid crosses can be performed Monohybrid and Dihybrid crosses can be performed using genetic traits located on chromosomes 1,2, 4.using genetic traits located on chromosomes 1,2, 4.

Sex-linked crossesSex-linked crosses contain traits that are controlled by contain traits that are controlled by genes located on the sex chromosomes ( chromosome genes located on the sex chromosomes ( chromosome #3). #3).

Wild Type (Normal Flies)Wild Type (Normal Flies)

Apterous Flies(no wings)

   

                                            

                                              

                                            

                                              

Vestigial (wings reduced)Vestigial (wings reduced)

Bar eyedBar eyed(narrow eyes)( sex-linked)(narrow eyes)( sex-linked)

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

White eyesWhite eyes

Curly wingsCurly wings