The Allele Frequency Research On Attached and Unattached Earlobes. at Southwest CTA. Michelle Perez. Madison Barton. Collin Marracco.

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1 The Allele Frequency Research On Attached and Unattached Earlobes at Southwest CTA Michelle Perez Madison Barton Collin Marracco Anthony Peccole Qinglan Guan Southwest CTA Biology H P8 February 28, 2013

2 Abstract A gene is a unit of hereditary information that is transferred by alleles from parent to offspring. This experiment was conducted to study the allele frequency in a single trait caused by a single gene. A survey was conducted to study the phenotype of a sample population of Homo sapiens. Further research was done to find the allele and genotype frequency for an unattached or attached earlobe. The chi-squared tests revealed that our frequencies were not equal and that we had found something significant. The data revealed that the allele frequency for the recessive allele was greater than the dominant allele. Furthermore, the genotype frequencies were not equal. The homozygous genotype tends to show up more frequently than the heterozygous genotype. In conclusion, the researchers of this study reject the null hypothesis, because some findings of significance among the three-genotype frequencies were discovered that could not be attributable to chance.

3 Introduction As humans, we are all diverse and unique. We have different genotypes that result in various types of phenotypes. These characterizations allow us to differentiate among each other and be one of a kind. Gregor Mendel helped the world realize how alleles, mitosis, and meiosis come together to provide an amount of combinations possible to an offspring. The scientific world has come a long way since then. With his research, we have discovered that alleles are alternate forms of a gene. Genes are located within our DNA that is wrapped and coiled in our chromosomes. There are two specific types of alleles, which are dominant and recessive. The allele frequency determines how frequent an allele expression arises in a population. In this case, we are testing the allele frequency of attached or unattached earlobes in Homo sapiens. We wanted to know if there is a significant difference in the allele frequency of the school population. Our research consisted of finding the visible phenotype and calculating the genotype with the gathered data. We decided to base our study around unattached or attached earlobes, because it involves a single gene. Testing this trait allows the experiment to produce accurate results while being fairly simple to accomplish. An unattached earlobe hangs freely and has space between the lobe and the body. It is a dominant trait while an attached earlobe is a recessive trait. An attached earlobe is attached to the body and has no space in between. Our dominant allele was expressed as capital E and our recessive allele was

4 represented by a lowercase e. The research sample of the SWCTA population was gathered from four grade levels and included both randomly selected females and males. According to the laws of natural selection, the dominant allele should become more frequently manifest, because it becomes favorable or advantageous overtime. The research null hypothesis is that there will be no significant difference among the allele frequency. Methods For this experiment, our hypothesis is that there will be no significant difference found between the observed and expected allele frequencies. The N population is the overall student enrollment of Southwest CTA. The total amount of students attending Southwest CTA is 1,400 people. We surveyed approximately ten percent of the population for a sample population (n) of 138 students. Among these students, we had an equal number of boys and girls surveyed. Sixty-nine girls and sixty-nine boys were tested. We also surveyed students from four grade levels, which included freshman, sophomores, juniors, and seniors. Thirty-five freshman and sophomores were tested, as well as thirty-four juniors and seniors. This gave us a grand total of one hundred and thirty-eight students. The procedure was fairly simple and easy. To organize and analyze our data, we recorded the results on a chart that was labeled with the categories attached and unattached. We color-coded it by putting the boys under the blue category and the girls in the pink category. We also had four different charts for each of the grade levels. During class, two of our group members went to various classrooms to survey the students. We

5 were able to survey all of the students in one class period. We started out surveying freshman, because they were the easiest to locate. After that, we went to random classrooms in hopes to find sophomores and upper classman. When we entered a classroom, we asked the teacher if we could take a quick survey. We explained that we were learning about alleles, traits, and genetics and that we were doing a scientific report on the allele frequency of a specific trait. After we received the permission to survey the students, we asked them to have their neighbor analyze their ear. Occasionally, we would come by and check peoples' ears, because they couldn't tell if it was attached or unattached. We went around the room gathering the data from the girls first. Then, we went around the room a second time to record the data from the boys. They would tell us their initials and whether their earlobe was attached or unattached. Finally, we thanked them for their participation and moved on to the next group of students. Eventually, we gathered all of the data we needed and started to analyze it. To analyze our data, we calculated the total amount of people with the attached and unattached earlobe phenotype. We used many different formulas like the chi-square and the Hardy Weinberg formula. Our group teamed up to figure out the frequencies of the dominant and recessive allele. With this information, we were able to find the genotype frequencies. Finally, we needed to use the chi-square formula to either reject or accept our hypothesis. We were able to use Quick-Calc to help us with the chi-square formula.

6 Results To find the frequency of the recessive allele, we divided the 51 people who had the recessive allele by 138. We got approximately 0.36 and took the square root to receive a recessive allele frequency of 0.6. We subtracted 0.6 from 1 to receive the dominant allele frequency for a result of 0.4. The recessive allele frequency was greater than the dominant allele frequency, but they were fairly close. We found the genotype frequencies and plugged all the numbers into the chi-square formula. Our results show that there is a significant difference in the allele frequencies. The chi-square results allowed us to reject our null hypothesis. The alpha loc a=0.05 was rejected because we found a significance of Therefore, we can claim that we found a significant difference in the allele frequency. Table 1: The table displays our trait as well as our alleles. While examining phenotypes, we had to distinguish attached earlobes from unattached. We did some research to determine which trait was dominant. We used a capital E to represent the unattached Trait Allele Allele Description Observed Frequency Expected Frequency Earlobes E Unattached e Attached phenotype. The recessive phenotype of attached earlobes was represented by a lowercase e. After doing the math and analyzing the data, we discovered that the allele frequency of the recessive allele was 0.6, and the dominant allele had an allele frequency of 0.4.

7 Table 2: We collected data by physically looking at peoples traits. The homozygous recessive genotype was easy to figure out. Sixty-six people had the recessive gene for attached earlobes. After that, we had to calculate the heterozygous and homozygous Genotype Observed Expected EE Ee ee dominant genotype. We multiplied the allele frequencies to find the percentage of each genotype. We then multiplied the percentage by the number of people studied to receive the number of people who had that genotype. The information on this table was plugged into the chi-square formula. Table 3: Out of the 138 people surveyed, 51 people had the recessive allele. The allele frequency for the recessive allele is 0.6, so the frequency for a homozygous recessive genotype was The remaining 87 people were dominant for the trait, so 0.64 was the frequency for an unattached earlobe genotype. We believed that there would be no significant difference among the genotypes, but the chi-square formula thought otherwise. Once we plugged in our data, the chi-square revealed that we had found a significant difference in our experiment. The chi-square value was with 2 degrees of freedom. The table value (a=0.0001) means there was significance in the allele frequencies. Therefore, we reject our null hypothesis.

8 Unattached Earlobe Attached earlobe Frequency Observed Frequency Expected Number Observed Number Expected Chi Squared Value with 2 degrees of freedom Chi Squared Table Value Accept or Reject Reject Discussion The overall results of our experiment allow us to reject our hypothesis. Therefore, there is a significant difference among the genotype frequencies. The a=0.05 indicates that, under the null hypothesis, our observations could have occurred by chance. Our rejection of the hypothesis indicates that there is a very small chance that the events could of occurred by chance. The homozygous genotypes were more presently seen than the heterozygous genotype. Out of the 138 people surveyed, 66 of them had the heterozygous genotype. This adds to the fact that alleles are inherited to an offspring, and that there are alternate forms of genes. Surprisingly, the recessive allele frequency overpowered the dominant allele frequency. Doing the same experiment in the next ten to twenty years could possibly alter the data and show that the population is in a state of evolution. The experiment and its data have taught us about genetics on a personal level. We were able to apply our knowledge in the real world with a real life situation. Overall, this research project has been a great learning experience. It taught us the process of a real experiment with real results. Acknowledgments

9 We would like to thank everyone who took part in this experiment. We couldn t have done this project at all without their cooperation. Overall, we would like to thank Mr. Goode for allowing us to do this project. It applied what we learned in the classroom to a real life experience. Furthermore, we would like to thank you for teaching us about genetics. Without your guidance, we wouldn t have the knowledge or the skills to complete this project. Finally, we would like to thank each other for being a good group and working together to get things done.