Genetics and Fruit Flies!

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

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

Adult fly body has 3 distinct regions A. Head-sight & smell B. Thorax attachment w/ 6 legs & 2 wings Abdomen (largest)-digestion, reproduction, & respiration

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

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

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

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

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

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

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

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

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!

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

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

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

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

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

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”

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

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

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

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

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

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”

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

Morgan’s Discovery

D. Other genetic manipulations Normal Fruit Fly

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

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

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

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

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