Title: Allele Shuffling of Single Gene Traits in Drosophila
Introduction/ Hypothesis: The purpose of this experiment was to determine if a single gene trait alleles of Drosophila are randomly shuffled to offspring. During this experiment, fruit fly inheritances were studied by looking at Drosophila with interesting characteristics and genetic mutations. Fruit flies are often used to study genetic process because they are hardy, they reproduce quickly, have a short life span, they are easily compacted and they have simple lifestyle and food requirements. Fruit flies traits are easily observed and identified because they only have four pairs of chromosomes. The nully hypotheses for this experiment is: if the p-value is greater than 5%, then allele shuffling can be said to be random.
Materials/ Methods:
For this experiment microscope, sorting brushes, sorting cards, fly morgue, petri dishes, wild-type flies, mutant flies, cultural vial with medium, foam plug, F1 cross vial and Fly Nap Kit were used.
Activity A:
In activity A, wild-type and mutant Drosophila will be anesthetized and given to the students in petri dishes. Wild-type flies were observed and examined with taking note of eye color and wing shape. Mutant types were then compared with the wild-type flies and Table 1 was filled out for the phenotype of each mutant and wild-type fly. Students then practice sexing the Drosophila. When done, flies were put in a morgue (a small vial of alcohol).
Activity B:
In Activity B, students were assigned the offspring (F1) of a cross between two of the four Drosophila observed in Activity 1 to study. F1 flies were examined and scored for phenotype and sex. The information was then put into Table 2. Cultural vials were then set up for F cross. One cup of instant Drosophila Medium and one cup of water was placed in the vial. When it solidified, 2-7 grains of yeast were put on top of the media. Five to six pairs of anesthetized males and females were put into a fresh cultural vial labeled “F1 cross” with the date and name of the student. After all F1 flies were scored, data was recorded, and F1 cross was set up, the rest of the flies were put in the morgue.
Activity C:
In Activity C, all the F1 adult flies were removed and placed in the morgue. This is so the F1 generation did not get mixed up with the F2 generation. To remove the F1 generation, students rapped the F1 cross vial on the table to knock the adult flies to the bottom. The plunge was quickly removed and the cross vial was put at the mouth of the empty vial. The vials were then inverted and students rapped the cross vial so the adult flies would fall into the bottom of the empty vial. Adult flies were then napped and placed in the morgue. The F2 generation was then observed in its larva form.
Activity D:
In Activity D, F2 adults were anesthetized (as explained in Activity C) and scored as the students sexed them and observed their phenotypes. When the data was collected, flies were then placed in the morgue. After all the data was collected, the class’s totals were combined and the results were recorded in Table 4.
Conclusion and Discussion:
The purpose of the “Allele Shuffling of Single Gene Traits in Drosophila” was to determine whether or not single gene trait alleles of Drosophila are randomly shuffled to offspring. The hypothesis for this experiment was: if the p-value is greater than 5%, then allele shuffling can be said to be random.
For Cross 1, the p values were greater than 5% which is not significant meaning the hypothesis was accepted. For Cross 2, the p values were less than 5% which is significant meaning the hypothesis was rejected. For Cross 3, the p values were less than 5% which is significant meaning the hypothesis was rejected.
The data suggests that the Allele Shuffling is not random. The data suggests this because two out of the three crosses do not support the hypothesis. This data also suggests that the shuffling could have been affected by unidentified variables.
Throughout the experiment there were several variables that could have affected the results. One variable is the temperature. The temperature was not kept constant through the weeks which could have affected the larval development. Another variable that could have affected the results is the accuracy of sexing of the flies. This was the students’ first attempt of sexing flies which could lead to a larger error of miscounting. The inaccuracy of sexing the flies could have an effect because fewer females in a cross could result in a smaller sample of the F1 generation, which would increase the chances of skewed data.
This experiment should be done again to determine if the allele shuffling is random or if unknown factors are contributing. A successful way to redo this experiment is to keep the flies at the same temperature the whole time period and to be more careful/ cautious while determining the sex of a fly. If the results come out to be the same, then the shuffling is random. If the results are different then it may just be unknown factors which affected the results.
