Mutagenic Effect of UV Exposure on Metabolic Activity of Fruit Flies (Drosophila
melanogaster)
Xin Gong
Department of Biological Sciences
Saddleback College
Mission Viejo, CA 92692
Ultraviolet light has been known to impact a living organisms either negatively, as
seen in plant growth, or positively, as seen in many forms of cancer. In fruit flies, UV
radiation has also been observed to have a negative effects on reproduction. This
experiment investigated the mutagenic effect of ultraviolet light on metabolic activity, using
fruit flies as the model organism. (State your hypothesis). Metabolic activity was
determined by how quickly the fruit flies regained consciousness after administration of
FlyNap® (What is Flynap?). Arousal times were measured after the flies had been were
exposed to UV light for a certain amount of time (include the different times used). Results
did not support the hypothesis and showed that longer exposure rates actually decreased
arousal time, suggesting that UV radiation has an activating effect on activated fruit fly
metabolism. These differences are were reflected by varying exposure times. Further
genetic testing would need to be done to confirm whether these differences are in fact a
result of mutagenesis, or if it is the result of a chemical change.
Introduction
Since mMetabolism is facilitated in large
part by enzymes, which are coded for by DNA,
iInducing a mutation in these genes can either
activate or inhibit translation of the metabolic
enzymes. In a hospital setting, variations in
metabolism of IV anesthetics, such as Propofol®,
administered in metered dosesm are commonly
observed in patients during surgery, which is why the
metabolic rates of each patient must be tested before
going into surgery. (The long sentence above is
confusing. Explain what you are trying to convey in a
few concise sentences rather than one long sentence).
Similar effects can be observed in fruit flies when
they are administered a metered dose of FlyNap®.
(Explain what Flynap is. Include some research you
have done on the product that relates to your
experiment). Individuals with similar genetic makeup
are expected to metabolize the anesthetic at a similar
rate. However, mutations in genes that control
metabolism can either increase or decrease the rate of
metabolism, depending on whether the mutation is
activating or inhibitory.
Drosophila melanogaster serves as a useful
model organism in biology due to its short generation
time as well as and its relatively simple karyogamy,
which consists of only three pairs of autosomes and
one pair of sex chromosomes,. This allows allowing
for easy genetic manipulation and testing. There have
been many compelling studies on the mutagenesis of
fruit flies in molecular genetics;. hHowever, not
many studies have been the done on the mutagenesis
of fruit flies in metabolism (Grigliatti, “Temperaturesensitive mutations in Drosophila melanogaster”).
(Fix citation: Last name, year published). (Explain
more about the studies that you have read that could
potentially contribute to your experiment). These
studies may bring to light many findings in the
metabolism of other organisms as well.
Since the major effect of UV radiation is to
create thymine dimers, which and therefore inhibit
DNA replication and transcription. , it was
hypothesized that UV radiation would is believed to
have an inhibitory effect on metabolic activity.
Longer exposure times to UV would is expected to
lead to longer arousal times following anesthesia.
(More background information needs to be
included to explain to the reader how it
supports the proposed experiment)
Materials and Methods
The following 40-mL vials with cotton
stoppers containing 15-20 flies with 10 mL of
nutrient media(Space)containing starch and active
yeast were prepared: a control, 5-, 10-, and 20second exposure groups. After being properly labeled,
each group of flies was were fully sedated with
Results
In contrast to the initial hypothesis, arousal
time decreased with increased exposure to UV
(Figure 1). While there was no significant difference
between the average arousal times between the 5- and
10- second groups, the flies in the control group took
significantly longer to regain consciousness while
those in the 20 second group took a significantly
shorter amount of time. Results of the ANOVA test
were significant, with a P value of 0.0015. (P=
0.0015, ANOVA with Bonferroni correction).
A paired post-hoc test determined that at a
95% confidence interval, there was no significant
difference between the control and 5-second groups,;
with a 95% confidence interval. hHowever, the
differences between the control and 10-second
groups and the control and 20-second groups were
significant (Table 1).
Arousal Time (in mins)
FlyNap®, an anesthetic mixture consisting of 50%
triethylamine, 25% ethanol, and 25% fragrances
(FlyNap® MSDS). FlyNap® administered through a
A Fly Wand suspended in the vial just below the plug
for approximately 45-90 seconds was used to
administer FlyNap®. To ensure that the last fly had
been anesthetized, the vial was gently tapped to
check for any movement.
The control group was not exposed to any
radiation. while tThe three variable groups were
exposed to UV light at 254 nm for 5, 10, and 20
seconds. Following After exposure, the flies were
incubated (at what temperature and where) for 3 days
to allow for recovery and fully express any mutations.
Flies were again knocked out with FlyNap® again
using the same procedure above (t0),and then
monitored vigilantly for the next few hours. Using a
stopwatch, the time of arousal for each fly was
recorded when the first sign movement was
observed(t1,2,3,…).The time it took for each individual
fly to regain consciousness, in minutes,was
calculated by subtracting t0fromtx , in minutes.
Results among the control and three
experimental groups were and analyzed by a single
factor analysis of variance (ANOVA)(Space)test
followed by a paired post-hoc test.
200
150
100
50
0
Control
5 sec
10 sec
20 sec
Exposure Groups
Figure 1: Bar graph displaying mean ± SEM arousal
time for control and experimental groups.
Table 1:Results of the post-hoc test (Bonferri
Correction) comparing the control group with the
three experimental groups *Results were significant
between the control and 10 second group and
between the control and 20 second group at α=0.05
and insignificant between the control and 20 second
groups*
Comparison
Significant?
(P <0.05?)
t
1: C & 5 sec
No
2.401
2: C & 10 sec
Yes
2.573
3: C & 20 sec
Yes
4.079
Discussion
In the time that it took for the fruit flies to
regain consciousness following after anesthesia from
FlyNap®, there were significant differences in
arousal times between the control group and the 10and 20- second group. However, while the initial
hypothesis was that lLonger exposure to UV light
would lead to was expected to induce longer arousal
times,. However, the results do not support the
hypothesis because the arousal time actually
shortened with longer exposure time. This suggests
that UV mutagenesis has an activating effect on
ability of the activates the fruit fly’s ability to
metabolize FlyNap®.
If mutagenesis occurred, the mutation may
have affected a gene coding for suppression of
metabolism, leading to an increase in metabolic
activity (Stryer,Biochemistry).However, it is not
entirely clear whether the significant increase in
metabolic activity is, in fact, due to a mutation or if it
is a result of a chemical alteration of the metabolic
enzymes within the fruit fly.(Explain how and why it
could be a chemical change). Further genetic testing
must be performed to determine whether this change
is genetic or chemical.
(Discuss more on why this topic is important to
research)
Literature Cited
Berg, J.; Tymoczko, J.; Stryer, L. Biochemistry.W. H.
Freeman and Company 2012.
Grigliatti, T.; Hall L., Rosenbluth, R.; Suzuki,
D. “Temperature-sensitive mutations in Drosophila
melanogaster.”Molecular and General Genetics.1973.
120 (2): 107-114.
Ziilstra, J.A.; Vogel, E.W. “Influence of inhibition of
the metabolic activation on the mutagenicity of some
nitrosamines, triazenes, hydrazines and seniciphylline
in Drosophila melanogaster.” Department of
Radiation Genetics and Chemical Mutagenesis,
University of Leiden, The Netherlands.1988 Nov;
202(1):251-67.
FlyNap® Material Safety Data Sheet
(A fifith source is needed)
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Department of Biological Sciences
Saddleback College, Mission Viejo, CA 92692
Author (s): Xin Gong
Title: Mutagenic Effect of UV Exposure on Metabolic Activity of Fruit Flies (Drosophila
melanogaster)
Summary
Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you
understood the paper.
The paper looked at the effects of UV light on fruit flies by measuring metabolic activity.
In the experiment, UV exposure was expected to decrease metabolic activity. A longer UV
exposure time was also predicted to increase arousal time. First, the fruit flies were sedated with
an anesthetic called Flytrap, and then each subject was exposed to UV light with different times.
Signs of mutation in the flies were observed after 3 days. This was done by having the flies
sedated once again to test metabolic activity. Metabolic activity was measured based on how
quick each fly gained consciousness and showed signs of any movement. Results of the
experiment didn’t support the hypothesis. Instead, the results showed the opposite. With longer
exposure times to UV decreased the arousal time.
General Comments
Generally explain the paper’s strengths and weaknesses and whether they are serious, or
important to our current state of knowledge.
The paper had many strengths. The idea of the experiment was excellent and interesting.
The general ideas were presented in an organized manner. Everything was in the correct order it
was supposed to be in. The layout of the paper was pleasant and easy to read off of. However,
the paper also had weaknesses. The paper lacked clarity in the introduction, methods, results and
discussion. There wasn’t enough research in the introduction that tied into the experiment. The
hypothesis wasn’t clearly stated. Certain words were not defined to give the reader a better
understanding of the project. The figure captions weren’t explained thoroughly. The discussion
didn’t discuss the importance of the project and why the world should care.
Technical Criticism
Review technical issues, organization and clarity. Provide a table of typographical errors,
grammatical errors, and minor textual problems. It's not the reviewer's job to copy Edit the
paper, mark the manuscript.
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This paper was a final version
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 This paper should be published as is
 This paper should be published with revision
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This paper was a rough draft