Drunken Flies and Alcohol Addiction Leyli Beheshti, Kinza Qureshi, and Lili Razavi Abstract Alcoholism is a serious problem around the world. Alcoholism can lead to many neuron damages if consumed in large amounts. Due to the resemblance between mammals and Drosophila melanogaster (fruit flies), fruit flies were used as a model to study the alcohol effects and also alcohol related behaviors in humans. It was hypothesized that there is an increase in alcohol tolerance throughout generations after fruit flies being exposed to ethanol. Ten samples of fruit flies were used for the parent generation and 45 fruit flies were used for the first generation; they were introduced into the inebriometer to measure the sensitivity of Drosophila to alcohol vapor. The time for the flies to fall down to the bottom of the column was noted for each generation. The mean time for the parent fruit flies were 28.693.080 minutes (SEM, n=10) and for the first generation were 10.600.0341 minutes (SEM, n=45). A one-tailed unpaired t-test (p-value=6.33x10-6) revealed a significant difference in the average time between the two generations. Our hypothesis says that there is an increase in alcohol tolerance throughout generations after fruit flies being exposed, but the result shows that there is a lower tolerance toward alcohol for the first generation. Possible explanation might be that the fruit flies were exposed to the alcohol too frequently leading to them still being intoxicated when the next dosage came.
Introduction Alcohol is considered one of the most consumed drugs in the world. People use alcohol to cope with the stress and struggles they experience throughout their lives and a non-controlled, continuous usage can ultimately lead to alcoholism. The social, economic, and personal abuse and addiction to alcohol is immeasurable. Alcohol actives certain areas of the brain that leads to an increase release of dopamine. Dopamine elevation provides a sense of pleasure and a positive reinforcement (Diamond and Gordan, 1997). There is not a perfect model organism that can depict exactly what can occur in humans when exposed to ethanol; however, they can model particular aspect of addiction. By researching about the effects of alcohol on fruit flies, scientists are able to find ways to control alcoholism in humans by getting a better understanding of how the brain reacts to ethanol and how to reverse its effects. Such an understanding will inevitably lead to better treatments for alcohol addiction (Rothenfluh, 2002). The fruit fly, Drosophila melanogaster, has been a leading model for aging research since early in the twentieth century. The benefits of using D. melanogaster for research include its short life span (1 to 2 months), inexpensive and easy to culture. Fruit flies have an advance nervous system (approximately 300,000 neurons) and are capable of various complex emotions (Hall, 1994; DeZazzo and Tully,1995; Hall, 1998; Sokolowski, 2001). Furthermore, they are easy to rear and have a generation time of only approximately 2 weeks, allowing scientists to explore certain traits and behaviors over a large number of generations in a very short period. Drosophila genome has revealed similarities between flies and mammals and can be a good animal model to study alcohol effects and behaviors (Adams et al. 2000). The natural habitat of fruit flies is fermenting plants, which usually have about 3% of alcohol. Fruit flies can metabolize alcohol for use of energy (Geer et al. 1993). When exposed to low dosages, fruit flies show signs of being energized and when exposed to higher dosages, the flies lose their balance and sedation (Moore, et al. 1998). By researching about the effects of alcohol on fruit flies, scientists are able to find ways to control alcoholism in humans by getting a better understanding of how the brain reacts to ethanol and how to reverse its effects. For our experiment we are going to see if there is an increase in tolerance in the first generation compared to the parent generation.
Methods and Materials The experiment took place over a 4 week period (from October 26, 2015 to November 18, 2015) in SM 244 at Saddleback College. Equipment was purchased from PetSmart in Laguna Niguel, CA and fruit flies were provided by the Biology department of Saddleback College. Two of the three soda bottles had the bottom portion cut off and the three bottles were stacked on top of each other to make a column. The bottle was taped together and three holes were cut into the column: two at the top bottle that were across from each other and one at the bottom one. A tube was placed from the Erlenmeyer flask to one of the holes at the top of the column. A tube with anhydrous calcium sulfate placed in-between was used in order to avoid condensation of the air mixture. Another tube was placed from the bottom of the column to the Stable systems flow meter that sucked out about 720 mL/min. The air pump was connected to the Erlenmeyer flask with tubing. The was cut and connected to each end of a small plastic tube that was placed into the rubber stopper which connected to each end of a small plastic tube that was placed into the ethanol. A picture of the set is seen below. 150 mL of ethanol was placed into the Erlenmeyer flask with the air stone and was heated while air was pumped through to create the ethanol - air mixture. An air flow pump was used to take 720 mL of air out in order to keep a constant amount of the ethanol - air mixture in the column. After waiting for 10 minutes, a syringe, with the bottom portion cut off, was inserted into the foam stopper and then placed into the tube that contained the fruit flies. Two fruit flies were placed into the syringe and then placed into the column and the timer started. The time was noted when a fly had fallen to the bottom of the column. After all the flies had fallen, the times were noted; the flies were placed into a new tube and were left to reproduce the next generation. After the new generation had grown into adults, they went through the same process and left to reproduce the next generation.
Figure 1. The picture above shows the set up of the project. Results The average time for the flies for each group to pass out is seen in Figure 1, which shows that the parent generation took much longer than the first generation to pass out. A one-tailed unpaired t-test was taken on the times from each group and was found that there is significant difference between the groups (p-value =6.33x10-6). The mean for the parent generation was 28.69 minutes with a standard error 3.080 minutes and 10.60 minutes with a standard error of 0.341 minutes for the second generation. The results reveal that the parent generation was more tolerant to the alcohol since they were able to survive in the ethanol air mixture for a longer period of time. The second generation passed out at a significantly lower time and has a smaller standard error compared to the parent generation. The results go against our hypothesis that the first generation will have a higher tolerance towards the mixture compared to the parent generation.
Figure 2. This graph shows the average time it took the fruit flies to pass out when exposed to ethanol. The parent generation took far longer than the first generation. Error bars are mean + SEM (p-value =6.33x10-6).
Discussion The purpose of this experiment was to see if there is an increase in alcohol tolerance from one generation to the next. Fruit flies were used as a model for humans since they have similarities in their genome and contain a variety of emotions (Hall, 1994; DeZazzo and Tully,1995; Hall, 1998; Adams et al. 2000; Sokolowski, 2001). Once exposed to ethanol, fruit flies have an increase in their sensitivity and tolerance towards alcohol which can affect their neurons (Scholz et al., 2000). The data collected revealed that the parent generation had a higher tolerance towards the ethanol-air mixture compared to the first generation. In this study, the data did not support our hypothesis, that there is an increase in alcohol tolerance throughout exposed generations. Although, this study revealed significant difference in the mean time between two generations. Our data collection opposed other studies on exposing fruit flies to the alcohol, and possible explanations might be that the fruit flies were exposed to the alcohol too frequently leading them being intoxicated when the next dosage came. Further study should be done to investigate the alcohol tolerance of exposed fruit flies through multiple generations by considering the fact of the exposed fruit flies are not intoxicated when their next dosage comes. It can be seen that the fly still contains some alcohol in their system is they are “hyperactive and disoriented” (Moore, et al. 1998). By considering this fact, the future generations can become more tolerant to alcohol than the previous generations. References Cited
Adams, M.D.; Celniker, S.E.; Holt,R.A 2000. The genome sequence Drosophila melanogaster. Science 287:2185-2195.
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Author (s): Beheshti, Qureshi, and Razavi
Title: Drunken Flies and Alcohol Addiction
Summary Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you understood the paper.
The purpose of this test was to discover the difference between the parent generation and the next generation’s ability to function under the effects of alcohol. The researchers hypothesized that the alcohol tolerance of the second generation would be greater than that of the parent generation. However, the data found didn’t support this hypothesis. This data reflects human alcohol consumption and the effects it can have. 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 is written with strong citation use. Outside research is referenced frequently. It’s seems much time was spent researching.
The methods for inebriating the flies’ needs to be better explained. It took several read- throughs to understand what was trying to be said.
This paper best talks about issues that are serious issues. Alcohol and its effects on humans or anything related to humans is information that should be gathered. Since humans seem to spend so much time drinking it.
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There were a few grammatical errors that are highlighted above and provided notes on, as well as several sentences that need to be re-worded a little.
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