Download Genetics of the Fruit Fly

Scientific Inquiry and Genetics with Fruit Flies
Use this Fruit Fly packet along with your Drosophila
Manual to help complete this lab activity.
(Do not write in this packet)
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Scientific Inquiry and Genetics with Fruit Flies
Lesson 1: Getting to Know Your Flies
Objectives
1.
2.
3.
4.
5.
Know components of the fruit fly life cycle
Understand why scientists use fruit flies for research
Identify traits that fruit flies have
Define phenotype
Identify males from females
Preparations & Materials (Week 1)
I. Prepare fly food and vial (#3)
a. To a vial add equal parts of banana flakes and water.
b. Add 3-5 pieces of yeast to the vial.
II. Obtain flies
a. Obtain 2 vials of different fly types. (Vial #1 and #2)
b. Use Flynap to anesthetize your flies.
c. Take your anesthetizing want and dip it into the Flynap. Press your
wand against the side of the Flynap container removing excess
Flynap.
d. Place the wand inside the vial, between the side and plug cap.
e. Watch your flies until all are “sleeping”.
f. Remove the wand and plug.
III. Prepare “crossing” vials and examine your flies.
a. One both vials contain “sleeping” flies you will transfer them into
your pre-made vial of food and yeast.
b. Dump flies onto 2 different sorting cards and gently examine them
by using the paintbrushes. What characteristics do they have?? Try
to distinguish between males and females.
c. Choose the “best” 5 flies form vial #1 and #2, and place them into
your pre-made vial (#3). ( YOU NEED- both males and females)
d. Make sure you take note of the flies you chose.
e. Label your vial #3, with masking tape that includes; your names,
flies crossed, date, and period. Lay vial on side.
IV. Clean up
a. Any flies not chosen for the cross needs to be placed in the
“fly morgue”.
b. Empty vials #1 and #2’s contents into the waste container.
c. Place vials in bucket to soak.
d. Put everything in your basket, just as you found it.
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Scientific Inquiry and Genetics with Fruit Flies
Lesson 2: The F1 Generation
Objectives:
1.Make proper observations of your new generation (F1).
2.Determine dominant versus recessive traits.
3. Reinforce identification of males and females
4. Understand “F1”
5. Classify/Group flies by phenotype
6.Revisit questions or hypotheses
7.Understand possible errors.
Activities
1. Review from the previous lesson, “What are some phenotypes of flies?”
and “What are some phenotypes that differentiate males from
females?”
Procedure
I. Prepare fly food and vial (#4)
a. To a vial add equal parts of banana flakes and water.
b. Add 3-5 pieces of yeast to the vial.
II. Observing the Flies:
a.
b.
c.
d.
Anesthetize flies by using Flynap. (See day 1 procedures)
Examine F1 flies with magnifying glass on sorting paper
Record number of different fly types (males, females, traits, etc)
Make observations and draw pictures
III. Prepare another “crossing” vial.
a. Keep the “best” 8 or so flies form your F1 generation and place
them into your pre-made vial (#4). (YOU NEED- both males and
females)
b. Make sure you take note of the flies you chose.
c. Label vial #4, with masking tape that includes; your names, flies
crossed, date, and period. Lay vial on side.
IV. Clean up
a. Any flies not chosen for the cross needs to be placed in the “fly
morgue”.
b. Empty vial #3’s contents into the waste container.
c. Place vials in bucket to soak.
d. Put everything in your basket, just as you found it.
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Scientific Inquiry and Genetics with Fruit Flies
Activities:
Lesson 3: The F2 Generation
1. Examine your F2 generation. What traits do you notice this time?
2. Record data and observations for this final generation.
3. List any other possible errors that could vary your results.
Conclusion Questions:
(Answer on a separate piece of paper)
1. Write one paragraph describing the overall procedures of the lab activity.
2. What State Standards were addressed in this activity? Use the Gold sheet
given to you at the beginning of the year.
3. What is YOUR definition for the following words?
a. dominant
b. recessive
c. phenotype
d. genotype
e. homozygous
f. heterozygous
g. carrier
h. gene
4. Punnett Square challenge.
Complete a dihybrid cross (2-traits) for the following genotypes.
AaBb x AaBa
A = small antennae
B = Bristle
a = large antennae
b = stubble
a. What is the percentage of getting a “small antennae and bristle” fly?
b. What is the percentage of getting a “large antennae and stubble” fly?
5. Eye color is linked to the sex chromosomes in drosophila. Cross a white
eyed male with a heterozygous female.
a. What are the chances of getting a white eyed female?
6. This lab experiment had many uncontrollable errors that could skew our
results. In one paragraph, explain at least 3 possible errors that may have
occurred throughout the activity.
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Scientific Inquiry and Genetics with Fruit Flies
Genetics Vocabulary
Dominant (allele):
An allele that expresses its phenotypic effect even when heterozygous with a
recessive allele; thus if A is a dominant over a, then A/A and A/a have the same
phenotype.
Dominant (phenotype):
The phenotype of a genotype containing the dominant allele; the parental
phenotype that is expressed in a heterozygote.
Recessive (allele):
An allele whose phenotypic effect is not expressed in a heterozygote.
Recessive (phenotype):
The phenotype of a homozygote for the recessive allele; the parental phenotype
that is not expressed in a heterozygote.
Phenotype:
(1) The form taken by some character (or group of characters) in a specific
individual.
(2) The detectable outward manifestations of a specific genotype.
Genotype:
The specific allelic composition of a cell – either of the entire cell or, more
commonly, of a certain gene or a set of genes.
Homozygous (gene pair):
A gene pair having identical alleles in both copies – for example, A/A.
Heterozygous (gene pair):
A gene pair having different alleles in the two chromosome sets of the diploid
individual – for example, A/a.
Carrier:
An individual who posses a mutant allele but does not express it in its phenotype,
because of a dominant allelic partner; thus, an individual of genotype A/a is a
carrier of a if there is complete dominance of A or a.
Gene:
The fundamental physical and functional unit of heredity, which carries
information from one generation to the next; a segment of DNA, composed of a
transcribed region and a regulatory sequence that make transcription possible.
DNA (deoxyribonucleic acid):
A double chain of linked nucleotides (having deoxyribose as their sugars); the
fundamental substance of which genes are composed.
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Scientific Inquiry and Genetics with Fruit Flies
The Fruit Fly Life Cycle
(Shown on the cover and pg. 8 of Manual)
Introduction: The fruit fly is an ideal organism for the study of genetics, in part because it has a
relatively fast life cycle. The fruit fly life cycle is approximately 10 days. This means that it takes 10
days for a fertilized egg to pass through the various stages of metamorphosis to reach the adult stage.
As with many other insects, the life cycle of the fruit fly consists of several distinct stages: egg, larva,
pupa, and adult.
Description of each fruit fly life cycle stage:
Egg: Fruit fly eggs are very small and can be hard to see. They can be seen on the surface of the food
in your vials as tiny (1 mm) specs, resembling small white grains of rice.
Larva (early stage): Early stage larvae can be seen crawling around the food in your vials. They are
several millimeters long and are whitish with tiny black mouthparts, which they use to eat the food in
the vial.
Larva (late stage): Late stage larvae (also known as “wandering” larvae) can be seen crawling up the
sides of the vials, out of the food. They are easy to see (about 4 mm in length), with whitish bodies and
black mouthparts.
Pupa: After late stage larvae have found a suitable location on the side of the vial, they form cocoons,
or pupae. Pupae are tan or brown in color, and are located on the sides of the vials. They do not move
around. During this life stage, the fly inside its pupal case loses its larval features and develops adult
features such as wings, legs, and eyes. Near the end of the pupa stage the pupa turns dark brown or
black in color, indicating that an adult fly is preparing to come out soon!. . .
Adult: Finally, the adult fly emerges from its pupal case. Adult flies have several body features that
are not found in eggs, larvae, or pupae, including eyes, wings, antennae, and legs. Adult flies can mate
with each other, and female adult flies will lay fertilized eggs down on the surface of the food, starting
the fruit fly life cycle anew once more!
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Scientific Inquiry and Genetics with Fruit Flies
Like people, flies come in many different varieties.
The eyes, antennae, bristles, body color, and wings can vary greatly from one
Drosophila strain to another. When one strain has red eyes and another strain
has white eyes, we say that the strains have different phenotypes.
Here are some pictures of different Drosophila strains: (Manual Pgs. 15-19)
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