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 Portfolio: The Study of Fruit Fly Genetics at City High School


ThreeRed's Fruit Fly Investigation

threered2, threered1, threered3, and threered4


The purpose of our fruit fly experiment was to learn about genetics which is the study of DNA, genes and traits.  We also studied mutations, which are the changing of an organism's genes and DNA sequence which makes the organism different than that of its species, and the effects of it on our flies.  The reason we used fruit flies is because they are easily cultured and only live for about two weeks.  They take up only a small space and females lay about 500 eggs in 10 days.  This gives lots of data and multiple generations in a short period of time.  Also, the mutations are quickly evident  because of easy to see phenotypes.


KINGDOM: Animalia- This phylum contains a variety of bilaterally symmetrical coelmats, including lobsters, crabs, spiders and insects. These animals have adapted to almost every environment on earth.

CLASS: Insecta

ORDER: Diptera

FAMILY: not sure

GENUS: Drosophila

SPECIES: Melanogaster



    Phenotypes are an organism's appearance or other detectable characteristic that results from the organism's genotype and the environment. Phenotype is either a total physical appearance and constitution or a specific manifestation of a trait just like size or eye color that could vary between individuals. Phenotypes are determined by genotype or by the identity of the alleles that an individual carries at one or more positions on the chromosomes. For example, If a fruit fly has red eyes and other normal characteristics it's phenotype is wild type. A common phenotype mutation in fruit flys is vestigal wings, which are designated by the genotype vg. A lot of phenotypes are determined by multiple genes and influenced by environmental factors. The identity of one or a few known alleles does not always enable prediction of the phenotype. Phenotypes are much easier to observe than genotypes. Therefore, classical genetics use phenotypes to deduce the functions of genes. Breeding experiments can also be checked as references. Geneticists then discovered that they were able to trace inheritance patterns without any knowledge of molecular biology.

P1 cross life cycle log

  3/16 V1- No larva, no dead flies

          V2- No larva, no dead flies

3/17 V1- No larva, no dead flies, no changes

        V2- Flies don't appear to be dead, but they have burrowed out of the medium and are moving very slowly inside the ditches they dug.

3/20 V1- Larva visible,no dead flies, burrows visible.

      V2-Larva visible, one possibly dead fly. Burrows visible.

3/21 V1- More larva visible on the sides of the vial. Pupas also visible. No dead flies.

       V2- More larva visible, no dead flies

3/23 V1- Lots of pupas and larvae

        V2- many pupa and larvae

3 /24 V1- Adult flies have been removed, tons of pupa, fewer larva, none ready to hatch.

        V2- adults removed, tons of pupas and larva, none ready o hatch.

3/27 V1- Pupas have hatched, mostly wild type flies fill the vial.

       V2- pupas have hatched, still several remain, and there is plenty of larvae

3/28 V1- There are even more flies and there are still several pupa. the pupa are getting darker             and will soon emerge.

        V2- several flies and pupa

3/30 V1 many flies, several pupa, some larva

        V2- tons of flies, several pupa, some larva. some dark pupa.

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Sexing the flies


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© 2006 threered4



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Click on an image to view larger version & data in a new window

© 2006


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Click on an image to view larger version & data in a new window

Drosophila melanogaster. Fruit fly vials. © 2006

F1 Cross Predictions

    We did a number of various test crosses to determine approximately how our F1 generation would turn out. We tested Autosomal crosses to see the differences between dominant and recessive, and different possible sex linked crosses. Here are some examples:

vg= Vestigial Wings      += Wild type

Autosomal Hypothesis 1(Vg Dominant): 

  vg vg
+vg +vg
+vg +vg

 100% of the offspring will be vestigial and heterozygous.

 Sex-Linked Hypothesis 1 (+ Dominant & Sex-linked):

  X+ Y
Xvg XvgX+ XvgY
Xvg XvgX+ XvgY


50% Wild, Heterozygous female          50% Vestigial Male


F1 outcomes

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Click on an image to view larger version & data in a new window

© 2006


F2 Cross Predictions

    Our predictions for the F2 fly cross revolved around the hypothesis that the vestigial wing mutation is autosomal recessive. We concluded this by observing that the likely genotype for F1 offspring was +vg. Meaning that the offspring were heterozygous wild in both sexes. Here are some example punnet squares of our F2 predictions.

 += Wild winged         vg= Vestigial winged


Vial 1 

  vg +
 + +vg ++
 vg vgvg vg+

Phenotypes for F2 Offspring:                     Genotypes for F2 Offspring:

75% Wild      25% Vestigial                    50% heterozygous +        25% Homozygous vg Recess.

                                                           25% Homozygous + Dominant


Vial 2

  + vg
 vg vg+ vgvg
+ ++ +vg

 Phenotypes for F2 Offspring:                        Genotypes for F2 Offspring:

75% Wild       25% Vestigial                         50% Heterozygous +   25% Homozygous vg Recess.

                                                                 25% Homozygous + Dominant


F2 Final Count

vial 1

 Overall Total


 Total Wild


 Total Vestigial


 Vial 2


 Overall Total


 Total Wild


Total Vestigial



Percent Error 

 Vial 1

Wild  252208.5  43.5 .208 20.8 20.8%
 Vestigial 26 69.5 43.5 .625 62.59 62.5%

Vial 2

Wild 147 137 10 .07 7
Vestigial  36 40 10.22 2222% 


    In the parent generation, the mutation vestigial is autosomal recessive, with a phenotype ratio of 3:1. Our results show a successful experiment. We had a very low percent error despite all the factors that could have resulted in poor numbers. For example, it was evident that we had contamination in vial one because we had flies with vestigal wings even though it was the F1 cross between wild type flies and heterozygous vestigal flies, which should have produced all wild type. In the end, this did not matter and the results still showed a low percent error. If we were to repeat this experiment, one thing we might try to do is monitor the parent crosses more closely to make sure we don't get any contamination of chromosomes. Still, in Vial one we only showed a 21% error with the wild type and a larger 63% error with the vestigal (208:70 vs. 252:26 as predicted). And in vial two, the wild type showed only a 7% error and the vestigial showed a 22% error.


    Though their lives were short, I'm sure we will all envy the simple bliss that was being a fly. To live in a world where your only obligation is to fly around and mate.


Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

© 2006


Learning Information

About This Page

Author: threered2, threered1, threered3, and threered4
Classroom Project: threered
city high school
Tucson, AZ USA

License: Tree of Life & Partners uses only - Version 1.0

Correspondence regarding this page should be directed to , city high school

 Treehouses are authored by students, teachers, science enthusiasts, or professional scientists. Anyone can sign up as a treehouse contributor and share their knowledge and enthusiasm about organisms. Treehouse contributions are checked for general accuracy and quality by teachers and ToL editors, but they are not usually reviewed by expert scientists. If you spot an error, please get in touch with the author or the teacher. For more information about quality control of Tree of Life content, see Status of Tree of Life Pages.

About This Portfolio

Molly Renner
city high school

University of Arizona

Lisa Schwartz
University of Arizona

Correspondence regarding this page should be directed to Molly Renner at , Kathryn Orzech at , and Lisa Schwartz at

All Rights Reserved.

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