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


The Fruit Fly of DOOM

threeblue1, threeblue2, and threeblue3


This particular project was focused on the genetic mutations of eye color and wing type. Because of the testing amounts and time restrictions, we needed a "guinea pig" that would reproduce fairly quickly, could be easily disposed of (Rabbits = bad idea) and could be easily identified to their Phenotypes because of their simple genetic makeup.  At the beginning of the experiment, we started with two vials. Vial 1 contained white females and wild males, six of each. Vial 2 contained wild females and white male, six of each.

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

Drosophila melanogaster. © 2006

Drosophila Melanogaster Classification

Kingdom: Animalia

Phylum: Arthropod (body segments have appendages, exoskeleton)

Class: insecta (head, thorax, abdomen)

Order: Diptera (one pair of wings, sucking piercing or lapping mouth parts)

Genus: Drosophila

Species: melangaster

Phenotypes Studied

In this experiment we have three different types of flies: Wild, Vestigial Wing, and White Eye. Wild characteristics are average, non-mutated species, namely, red eyes and full, folded wings. Vestigial wings are a mutation where the wings don't develop properly and are shriveled and deformed. The white eye mutation causes the wild red eye of the fly to become a lighter color that is more of and off-white or tan than true white.        

The two we will be using are Wild eye (represented by a +) and White eye (represented by a w).

Group Life Cycle Log

Date  Entry
Flies are expanded to new cultures
No sign of larvae. Medium dry; added water.
Larvae in early stages, burrowing and eating
Larvae have grown and some progressed to pupae stage.
No noticeable growth in larvae. number of pupae increased to 20,. 15 new adult flies.
Close to 30 flies. Equal larvae and pupae. None hatching, Few adult flies dead.
3/10 Pupae almost done hatching. Almost all Larvae progressed
3/16 Start of main experiment. Our group has our own fruitflies. Chosen 6 male+ to be bred with 6 femalew (vial 1); also 6 malew to be bred with 6 female+(vial 2). Ready to begin P1 Cross.
No noticeable signs of larvae. 2 male, deceased. Flies appear edgy.
Still no signs of larvae. 4 malew deceased. Believe medium is too dry; going to add more water to both vials
Vial 1 has signs of larval activity. 4 currently seen, maybe more in center of medium. No signs of larvae in vial 2. No new deaths.
Larvae in vial 1 have progressed to pupae stage. Vial two has gained new larvae. Euthanized adult flies.
Last of vial 1 larvae going into pupae stage. Vial 2 has gained new pupae.

 Vial 1 : Newly hatched flies. Most of them are wild eye. Still a lot of pupae to hatch.

Vial 2  : One hatched fly. A few pupae ready to hatch. Ground looks dry & broken up; probable cause is larvae burrowing.


Vial 1 : Many flies have hatched. Few pupae close to hatching.

Vial 2 : Number of flies has nearly doubled.


Vial 1 : Almost all flies have hatched; many of which are wild eye, few white eyed. Approx. 20 more pupae to hatch.

Vial 2 : One pupa left to hatch. One fly is white eyed while the others are wild eye.

4/3   Time to begin F2 cross. Unfortunately, it appears our F1 flies were contaminated. Due to this only our male flies for planned crosses are useable. To remedy this, we have obtained female flies from a group that is very similar to ours. We have transferred them to their new vial's and have cleared the rest.

 Vial 1 : Medium starting to dry out. Most flies dead, only a few live specimens.

 Vial 2 : No flies. A pink dome in the center of the vial. It almost looks like pink cottage cheese, or a very small brain. We believe it to be an extreme bacterial infection. We have no choice but to dispose of it.

4/21  Vial 1 : Few flies hatched from pupae. It appears that not many larvae survived.
4/24 Vial 1 : 2 flies, both white eye. One escapes the other is male.

 Sexing the Flies

During this time of sexing the flies we had to do the following:

1.Take both vials of flies and tap the bottom downwards

2.Prepare fly nap by dipping the black Q-TIP looking object into small bottle of fly nap

3.Tap the bottom of the vials downwards and quickly pinch the foam in the vial allowing enough room for the Q-TIP like object to slide in easily (TRY NOT TO TOUCH FLY NAP TO THE VIAL OR THE FOAM).

4.Wait about 3 to 4 minutes for all of the flys to fall to the bottom of the vail and then they are ready to be poured out on to a 3x5 note card divided saying on one side male and the other female

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

5.Once scattered on the 3x5 note card flip over flies to reveal there stomachs to the sky.

6.The males often have a slightly larger dot on the bottom of the abdomen; the females do not. (This is harder to tell on newly hatched adults)

7. Then place the females on the female side and the males on the male side. 

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 threeblue1

F1 Predictions

If the mutation for white is sex-linked recessive, and wild is dominant,
Then the genotypes will be…

Female Mutation:
50% XwX+
50% XwY

Male Mutation:
50% XwX+
50% XwY

 Here is a Punnet square showing a cross between a white-eyed female and a wild-eyed male. (Sex-Linked white-eye Recessive, as in the Hypothesis.)


Xw X+

Xw Y
Xw X+
Xw Y

Here is the same square, but this time the cross is between a white-eyed male, and a wild-eyed female:

  Xw Y
 X+  Xw X+ X+ Y
 Xt  Xw X+ X+ Y

F1 Outcomes

 Vial 1 cross: White eye Female X Wild eye Male

Male Phenotype: White eye

Likely Genotype: XwY

Female Phenotype: Wild eye

Likely Genotype: X+Xw

Vial 2 cross: Wild eye Female X White eye Male

Male Phenotype: Wild eye

Likely Genotype:X+Y

Female Phenotype: Wild eye

Likely Genotype:X+Xw

We have determined the genotype based on the supported guess that our variant phenotype is sex-linked recessive.

F2 Predictions

Our hypothesis about our mutation was that it was sex linked recessive.

vial 1 f1 cross=male w genotype = XwY X female, geno= XwX+

 Xw  XwXw  XwY
X+   X+Xw  X+Y

%Phenotypes in f2

25% white eyes homozygous female 

25% wild eyes heterozygous female

25% white eyes male

25% wild eyes male

%Genotypes in f2

25% XwXw

25% XwY

25% X+Xw

25% X,+Y

vial 2 f1 cross = female w genotype= XwXw X male, genoX+Y

Xw   XwX+  XwY
Xw  XwX+  XwY

 % Phenotypes in f1

50% white eye hetero female

50% white eye homo male

%Genotype in f1

50% XwX+ female

50%XwY male 

F2 Final Count 

date F2 counted female wild male wild female w male w
4/17 1 0 3 2
4/19 1 1 0 3
4/21 1 1 0 0
4/24 0 0 0 1

overall total

from vial 1


total female +


total male +


total female W


total male W


Percent of Error

Phenotype  Observed
 Expected |O-E|  |O-E|/E
% of Error
Male w
 6  3.5  2.5  .71  71%
Female w
 3 3.5  .5  .14 14% 
Male +
 2 3.5 1.5  .43  43% 
Female +
3.5  .5  .14  14%


Our hypothesis was that if the White-eye allele was sex-linked recessive, then 50% would be White-eyed, and 50% would be wild-eyed. Unfortunately, our data was inconclusive to our hypothesis. Because of a combination of bad luck and mistakes on our part, several elements of our data were skewed. During the week of April 17, some sort of bacteria developed in vial 2, killing all of our flies. Also, because of some irrational patterns in the offspring, we believe that not all of the females were virgins. To come to a clear conclusion, we would need to re-test the experiment.


Vial 1:

Date of birth: February 27th, 2006
Date of death: April 24th, 2006

Over the term of this project, we have come to know Vial 1, fondly referred to as 'The little survivors', very well. Although we often did not know the outcome, Vial 1 really pulled through, with the two flies recovered. (Even though one escaped.)

Vial 2:

Date of birth: February 27th, 2006
Date of death: April 17th, 2006
We wish that this Vial could have had more time on earth, but lo, how they were overcome. We mourn their untimely death via brain damage.

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


Learning Information

About This Page

Author: threeblue1, threeblue2, and threeblue3
Classroom Project: threeblue
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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