Drosophila Melanogaster Report
Caylin Ballard
Introduction:
The Senior Advanced Biology class was instructed to perform an experiment over the
Drosophila Melanogaster, also known as the common fruit fly. The purpose of the experiment
was to test probability against reality of wing traits in the F1 and F2 generations. The experiment
conducted pertained to apterous (recessive) and wild (dominant) fruit flies. Class members were
given vials each containing the initial parent generation. Every twelve hours students checked the
vials to collect virgins. Once an amount of virgins were collected from apterous and wild,
crosses were made. After the cross was made and larvae appeared, the parents were removed,
counted, and placed in a F1 x F1 vial. These steps continued into the F2 generation. Punnett
squares were used to determine the probability of the outcome of traits.
Materials and Methods:
The parent generation flies are sorted and then placed in vials containing fly medium,
water, and a few granules of yeast. Students received flynap to aid in checking the fly’s sex
under the digital microscope. Students were also given a sorting brush to help sort the flies into
males and females during observation. The vials were stored at room temperature to ensure the
flies were in a stable environment. After sexing the flies approximately fifteen females were
placed in a separate vial and the males were humanely destroyed. The virgin female vials were
sealed for two weeks to ensure that they were virgins. These virgins were then crossed with the
opposite trait. Apterous females were placed with wild males and wild females were placed with
apterous males, which produced the F1 generation. Roughly two hundred flies of the F1
generation were collected from each lineage of crosses. The F1xF1 vials were then checked
every twelve hours. Once larvae appeared on the sides of the vials the parents were then placed
in a back-up vial. The offspring from the larvae of the F1xF1 vial made up the F2 generation. As
the F2 generation hatched, they were counted and humanely destroyed. That process continued
until a total of five hundred flies from each cross were recorded.
Results and Discussion(final)The purpose for this experiment was to determine the probability from the reality
of phenotypes of the drosophila melanogaster. Before the experiment began it was hypothesized
that the F1 generation would have a 4.0 ratio of winged dominant phenotype, which means that
100% of the flies would be winged. The reality of the experiment showed a 99.2% phenotype of
wild. (11 apterous, 854 wild) There were a total of 1,355 F1 generation flies. Below are the
graphs and Punnett squares displaying the probability and reality of the genotypes and
phenotypes of the experiment.
Reality
0.8%
P1
Cross
Wild
Winged
Apterous
99.2%
100%
W W
w Ww Ww
w Ww Ww
Probability
Continuing the experiment, a cross was made between the F1 and F1 generations to
create the F2 generation. A total of 1,122 flies were collected. It was hypothesized that 75%
would have the dominant winged phenotype, and 25% would have the recessive non-winged
phenotype. In reality 98% received the dominant winged trait, and only 2% received the
recessive non- winged trait.
Reality
Wild
Probability
Apterous
Wild
2%
Apterous
25%
75%
98%
F1
Cross
W
W
w
WW Ww
Ww ww
w
ConclusionIn conclusion to this experiment the hypothesis for the F1 generation was proven correct.
Flies carrying the winged phenotype were 99.2% while flies carrying the apterous phenotype
were 0.8%. In the F2 generation the hypothesis was proven incorrect. Flies carrying the winged
phenotype were 98.0% while flies carrying the apterous phenotype were 2.0%. The hypothesis
was a 75% to 25% probability. However, the experiment went wrong with one of the apterous ♀
and wild ♂ cross vials causing the experiment to drastically change, along with the results.
Acknowledgements
I would like to thank Ms. Phillips for being the BEST Bio II teacher around and for helping us
and staying sane with the project even though we let out billions of flies in the lab.  I would
also like to thank my parents for not kicking me outside when I would let out flies in the house.
Even though all the flies in the house weren’t mine! ☻