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


Three Green Fly Group's Investigation

threegreen3, threegreen1, threegreen2, and threegreen4


The purpose of this experiment is to learn about heredity in genetics through the study of fruit flies. The reasoning behind using fruit flies was because fruit flies have fairly obvious mutations, reproduce quickly, have a large number of offspring, and are much easier to work with in a science classroom than some other animals.


Kingdom: Animalia

Phylum: Arthropoda - exo-skeleton, molting,open circulatory systems, segmented body parts, cephalization

Class: Insecta - antennae, six legs, mandibles, 3 body segments

Order: Diptera -1 pair of wings sucking, lapping, piercing mouth parts

Family: Drosophilidae

Genus: Drosophila

Species: melanogaster


Wild phenotype - is the normal mutation of a fruit fly with normal wings and normal red eyes

Vestigial phenotype - the wings on this mutation are short and wrinkled.

Recessive sex-linked white phenotype - white eye mutation of a fruit fly.

Group Life Cycle Log

Date      Observations

3/16       Not enough flies mating no larvae

3/17       Still not enough flies, no flies have died still no larvae

3/20       Larvae, eggs, 1 dead fly, no pupas

3/21       Lots of larvae, 15 visible, 1 visible egg, no more flies have died, the larvae in varying   stages.

3/23       There are lots of pupae and some parent flies and larvae that are ready to become pupae

3/24       With the parents gone, the larvae are living large. The pupae, on the other hand are just lying around, lazy teenagers.

Sexing the Flies

We found it was time to sex flies for the first time. This was a practice run, with no real consequence for failure (later, we had to sex them to properly distribute males and females of the correct type into vials: ( Now THAT was serious!), but it was still gross.

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

    We had to knock them out, so we used a substance called FlyNap.

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

We inserted an absorbant wand filled with the potion into the vial. The flies were asleep in two minutes.

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

Once they were FlyNappin', we shook them out onto a card. We then looked at them under a magnifying lens, determined their gender, then we killed them. In rubbing alcohol.

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

When we did it for real, we followed the same procedure, except that, instead of murdering them, we distributed the correct gender/type combinations into the correct vials. Then came the fly sex. And now we have many happy larvae. Wait... make that many happy flies, a bunch of pupae, and a small scattering of larvae! Go miracles of nature! But soon, too soon, the hatchlings grew, were sexed, and ritualistically murdered.  And now we know the truth. Rated R.

F1 predictions 

We made predictions about whether the traits would be dominant or recessive. We also made predictions about whether traits were sex-linked or if we switched the dominant and recessive genes about what outcomes would be.

vg=vestigial; vestigial is where the wings are not fully developed, they are usually crinkled or smaller than the normal wings. + = wild; wild is just a normal fly, they have normal wings and red eyes.

  vg vg
vg+ vg+
vg+ vg+
In this punnent square we are showing that vg is a dominant gene and + is a recessive gene therefore the phenotypes we are expecting looking at the punnent square are 100% vg.
  X+ Y
Xvg XvgX+ XvgY
Xvg XvgX+ XvgY
In this punnent square, the phenotype is 50% vg male and 50% carrier female. So therefore the males will have the vg mutation and the females will just be carrying the mutation for the next generation

F1 outcomes 


 vg vg
 +  +vg +vg
 +  +vg  +vg

Phenotypes=100% vg

F2 Predictions 


 + vg


 ++ +vg
 vg +vg
Phenotypes Vial1 f2
 75% wild
25% vestigial


 + vg
 + ++
 vg +vg
 f2 Phenotypes vial 2
25% homozygous wild
50% heterozygous wild
25% homozygous vestigial

 F2 Outcomes

  overall  total
wild females
total +
wild males
 vg female
 vg male
total vg
 vial 1
 27  25 52
vial 2

  vials 1&2

 + vg
 +  ++ +vg 
 f2 percentages vial 1
 vg  =15%
 f2 percentages vial 2
 vg  =23%

F2 fly counts 

 Vial 1
 Overall total
 Total Female +
Total Male +
 Total Female VG
Total Male VG
   347 95
Vial 2   Overall total  Total Female +
 Total Male +
  Total Female VG  Total Male VG

Observed versus Expected

Phenotype          Observed      Expected     (O-E)    (O-E)/E     X100     %error

vial 1 - wild         295              260.25         34.75    0.13352     13.35     13.35%

vestigial              52                86.75         -34.75   -0.40057    -40.05      40.05%

vial2 -  wild         168              164.25          3.75     0.02283     2.283      2.283%

vestigial              51               54.75           -3.75    -0.06849     -6.849     6.849% 

Observed and Expected and the Hypothesis

The wild expected less than observed and the vestigial phenotype expected more than the observed number so that supports the autosomal recessive hypothesis.

Percent error that is too high for the hypothesis:

-40% in vial one phenotype vestigial seems too high for the hypothesis compared to vial two for the same phenotype.

Factors for high percent error:
mishandling vials led to death, and letting flies out of the vial
accuracy- observe more carefully


In conclusion we hypothesized that the phenotypes for the flies would end up at 75% wild type and 25% vestigial for our F2 generation. According to our data and our error percentage we were right, because we only had an error percentage of 2% and 6% on our vial 2 flies which means that we were 98% and 94% correct. In addition to our incredibly accurate results, the data was a bit skewed because not all of the flies accounted for/. For instance flies that died or escaped during the napping process. But the next time we do this we will all be better at the napping process because of all of our experience.

Eulogy for the Flies

Our flies were not human. They were not even vertebrates. But they came as close to our hearts as they could through the walls of a glass tube. They touched our hearts in a way only something that never made physical contact with us could. We loved them like our own children. We put them to sleep, determined their gender with a magnifying lens, then dumped them into rubbing alcohol, killing them instantly. We commit them to the void and such and so forth but nigh time is short. Lunch is in about ten minutes. Amen

Learning Information

About This Page

Author: threegreen3, threegreen1, threegreen2, and threegreen4
Classroom Project: threegreen
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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