Download Allele Frequency Research At SWCTA Into Unattached Earlobes-P8T4

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
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.
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
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
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.
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 0.0001. 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
Observed
Frequency
Expected
Frequency
Description
Earlobes
E
Unattached
0.4
0.5
e
Attached
0.6
0.5
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.
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
21
46
Ee
66
46
ee
51
46
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 0.36. 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 22.825 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.
Frequency Frequency Number Number Chi
Observed Expected Observed Expected Squared
Value
Unattached 0.64
Earlobe
0.5
87
69
Attached
earlobe
0.5
51
69
0.36
22.825
with 2
degrees
of
freedom
Chi
Squared
Table
Value
Accept
or
Reject
0.0001
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
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.