1. Genetics and Fruit Flies!

2. Fruit fly scientific name-Drosophila melanogaster
A. Drosophila-“dew lover” (dew-sugar)
Melanogaster -“black belly”
“Black bellied dew lover”

3. Diptera - 87,000 species of flies, gnats, & mosquitoes
A. Phylum -Arthropoda
B. Class - Insecta
C. Order - Diptera (two winged)

4. Adult fly body has 3 distinct regions
A. Head-sight & smell
B. Thorax attachment w/ 6 legs & wings
Abdomen (largest)-digestion, reproduction, & respiration

5. IV. Can find them … A. Summer time B. Swarming garbage pails
C. Swarming decaying fruit
D. Mistaken for gnats!

6. V. Characteristics A. Taste receptor hairs-front legs
1. Taste food by walking on it!!

7. B. “Sponging” mouth parts
1. Food must be in liquid form
2. Regurgitate digestive enzymes breaks down food-sponge it up!

8. Ocelli- scores of tiny, 6-sided facets in eyes
Can’t see sharp images but good at detecting movement!
Humans see ~
1000 x’s better

9. 3 simple orange eyes of Drosophila
Boosters increase sensitivity of compound eyes to light

10. Antennae - 2 “feelers” head
Movable segmented organs-touch, smell, & taste
Locate decaying fruit by “smell”
a. Alcohol produced by fermentation

11. Hairs on body, legs, wings, & antenna
1. Very sensitive to air & vibrations

12. G. Sex comb on male flies: dark hairs on front legs
Attract female attention before mating

13. H. Chitin - external skeleton
1. Muscles attached to skeletons on inside
2. Do not fatigue easily
3. Can fly continuously
=6 hours!
4. Can fly ~ 2.5 mph!
5. Wings beat
~ 250 times/second!

14. Haltere - club-shaped organ below ea. wing
1. Balancing instruments
2. Wing moves up & haltere moves down
3. If removed, “flies” in circles!

15. VI. Food in vials mainly for larvae but adults eat it too!
A. Wheat, oat, soy flour, vitamins, salt, iron, sugar, preservatives, & yeast
B. Food coloring: easier to see larvae/ eggs

16. VII. Female fly can’t mate until ~ 10 - 12 hours pupa form
A. Pick females < 10 hrs old-virgins
B. Once mated female retains sperm & lays fertile eggs

17. C. Drosophila egg 1. 0.2 mm long, shiny, white, translucent
2. Outer membrane pattern of hexagonal markings under a microscope
3. Eggs hatch
Breathing
apparatus
For larva

18. D. Small, white worm-like larva
1. Three/four days eating food
2. Stage lasts up to 5 days
3. Shed outer covering (cuticle) twice
4. Instar - stage in btwn shedding

19. E. Larva-ready pupa crawls out of food
1. Outer layer darkens: hard-puparium
2. Worm-like larva changes into adult
3-5 days-process metamorphosis: “change in form”

20. F. Young fly 1st emerges from puparium
1. Almost white, abdomen very long
2. Head elongated,wings are wet & crumpled
3. Slowly forms adult features-few hours
4. Small flies do NOT grow into large flies
5. Size = size when emerge from puparium
6. Different sized flies= different species

21. G. Life cycle 1. Short, lasting 10-15 days, depends on temp
2. 30 generations of flies –studied in 1yr!

22. VIII. Drosophila -ideal animal for genetics research
A. Easy to care for
B. Small jars /vials containing special food
FEMALE
MALE
C. Easy to tell males /females

23. D. Many offspring
E. During ~ 2 month lifetime = several hundred flies

24. IX. 100’s of genetic variations in Drosophila
A. Affect body color, shape, pattern of body hairs, eye color & shape, & wing structure

25. B. Used in genetic studies since 1909
1. Thomas Hunt Morgan made genetic history
a. Mated male fly w/white eyes with red eyed female
b. New flies red eyes (showed red eyes dominance)
c. F2 gen - 1/4 flies white-eye/males
d.1st genetic trait to be “sex-linked”

26. C. Discovery - 1 pair chromosomes determines sex
1. Fruit flies 8 chromosomes/body cell
2. Morgan found males w/ bent chromosome
3. Called bent chromosome “Y” and the other one, “X”
Therefore, males-XY & females-XX

27. Morgan’s Discovery

28. D. Other genetic manipulations
Normal Fruit Fly

29. X. Important commercially
A. Gov. spent millions to keep pest under
control in CA & FL
B. Mediterranean fruit fly - Med Fly
C. Looks like house fly w/orange/black markings
D. If females are found destroy crop to keep insect from establishing breeding population

30. XI. Our Experiment Eye color is sex-linked in fruit flies
1. Red (wild type) dominant over white (mutant)

31. Carolina Supply company provided P generation
White eyed females crossed with red eyed males
What is their genotype?
a. R = red eye r = white eye
b. XrXr ♀ XRY ♂
3. What flies were transferred to your vials (the F1 generation?) XR Y Xr
XRXr
XrY Xr
XRXr
XrY
1 red eye female: 1 white eye male

32. Cross two F1 flies to predict your F2 generation
1. XRXr ♀ x XrY ♂ Xr Y
Phenotypic ratio? XR
1 Red ♀ (25%) :
1 Red ♂ (25%) :
1 white ♀ (25%) :
1 white ♂ (25%)
XRXr
XRY Xr
XrXr
XrY

33. XII. Conclusions and vocab
List 5 facts about fruit flies!
List and define all vocab terms!