Download - Mendelian Genetics Lab
Mendelian Genetics Lab
Tyler Harvey
Lab Partner: Mason Youngblood
Dr. William Alexander
10:00 Lecture
Harvey 2
Introduction:
Encyclopedia Britannica defines genetics as “the study of genetics or genes in
particular.” One important field of study in genetics is that of molecular genetics pathology, or
the study, diagnosis, and treatment of genetic disorders and diseases.
One such genetic disorder in which great strides have been made in the research and
possible treatments of is celiac disease. Celiac disease is a hereditary, genetic disorder that
causes those affected by it to not be able to tolerate the protein gluten, which found in wheat,
barley, malt and rye flours. The common misconception is that this disorder is caused by a
genetic disorder which is not the case. It is actually an autoimmune digestive disorder caused by
a specific type of surface cell receptor protein found on antigen presenting cells called HLA-DQ.
The gene that codes for this receptor protein is found on the short arm of the sixth
chromosome. Because of this, the specific locus on the chromosome has come to be known as
CELIAC1. About 95% of celiac patients have either the DQ2 or DQ8 isoform of the HLA-DQ
receptor. These receptors are thought to be linked to the disease because they bind more tightly
to the gliadin peptides found in grains and trigger the activation of T lymphocytes that begin the
autoimmune process.
Currently, the only way to deal with celiac disease is to totally eliminate gluten
containing foods from the patient’s diet. However, recent studies have shown that certain
combinations of enzymes have the ability to degrade certain peptides which may allow celiac
patients to consume gluten safely. These treatments, though, are only in the experimental stages.
In the future, study of genetics and genetic pathology may to a better understanding of the
relationship between genes and the attributes of cells that they code for. This could very well
lead to the discovery of treatments or even cures for celiac disease and other genetic disorders.
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Methods and Materials:
The group was given an ear of 3:1 genetic corn from Carolina Biological Supply by Dr.
William Alexander. Tyler Harvey counted the number of purple and yellow kernels in each row
on the corn while Mason Youngblood recorded the data in his notebook.
The group was then given an ear of 9:3:3:1 genetic corn from Carolina Biological Supply
by Dr. William Alexander. This time, Tyler Harvey counted the number of purple smooth, purple
wrinkled, yellow smooth, and yellow wrinkled kernels in each row while Mason Youngblood
recorded the data in his notebook.
After all the data was recorded, the expected frequencies of each phenotype were
calculated by setting the total number of phenotypes to the 3:1 and 9:3:3:1 ratios. Once the
expected frequencies were calculated, a chi square test was performed for each test with a TI-83
calculator using the expected and observed frequencies.
Results:
Corn Cob #1:
Null Hypothesis: There will be a 3:1 ratio of purple kernels to yellow kernels in an ear of 3:1
genetic corn from Carolina Biological Supply
Alternate Hypothesis: There will not be a 3:1 ratio of purple kernels to yellow kernels in an ear
of 3:1 genetic corn from Carolina Biological Supply
Ratio of Phenotypes on an ear of 3:1 Genetic Corn from Carolina Biological Supply
Observed Expected
Purple 452 464.25
Yellow 167 154.75
Chi Square Test:
χ2= ∑ [(o-e)
2 /e]
χ2= [(452-464.25)
2/464.25] + [(167/154.75)
2/154.75]
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χ2= 1.292945611
Df= k-1 = 2-1 = 1
At a level of significance of 0.05 and with 1 degree of freedom, the critical value of the chi-
square distribution is 3.814. Since the calculated value of 1.292945611 is less than the critical
value, I accept the null hypothesis that there will be a 3:1 ratio of purple kernels to yellow
kernels on a 3:1 ear of genetic corn from Carolina Biological Supply.
Corn Cob #2:
Null Hypothesis: There will be a 9:3:3:1 ratio of purple smooth kernels to purple wrinkled
kernels to yellow smooth kernels to yellow wrinkled kernels in a 9:3:3:1 ear of genetic corn from
Carolina Biological Supply.
Alternate Hypothesis: There will not be a 9:3:3:1 ratio of purple smooth kernels to purple
wrinkled kernels to yellow smooth kernels to yellow wrinkled kernels in a 9:3:3:1 ear of genetic
corn from Carolina Biological Supply.
Ratio of Phenotypes on an ear of 9:3:3:1 Genetic Corn from Carolina Biological Supply
Observed Expected
Purple Smooth 257 248.625 Purple Wrinkled 75 82.875 Yellow Smooth 83 82.875 Yellow Wrinkled 27 27.625
Chi Square Test:
χ2= ∑ [(o-e)
2 /e]
χ2= [(257-248.625)
2 / 248.625] + [(75-82.875)
2 / 82.875] + [(83-82.875)
2 / 82.875] + [(27-
27.625)2 / 27.625]
χ2= 1.044746104
Df= k-1=4-1=3
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At a level of significance of 0.05 and with 3 degrees of freedom, the critical value of the chi-
square distribution is 7.895. Since the calculated value of 1.044746104 is less than the critical
value, I accept the null hypothesis that there will be a 9:3:3:1 ratio of purple smooth kernels to
purple wrinkled kernels to yellow smooth kernels to yellow wrinkled kernels in a 9:3:3:1 ear of
genetic corn from Carolina Biological Supply.
Discussion and Conclusions:
For the 3:1 ear of genetic corn we found that the calculated chi square value was less than
the critical value at a level of significance of .05 and with 1 degree of freedom. We accept the
null hypothesis that there is a 3:1 ratio of purple kernels to yellow kernels in an ear of 3:1
genetic corn from Carolina Biological Supply and conclude that the only significant factor acting
in this experiment was chance.
For the 9:3:3:1 ear of genetic corn we found that the calculated chi square value was less
than the critical value at a level of significance of .05 and with 3 degrees of freedom. We accept
the null hypothesis that there is a 9:3:3:1 ratio of purple smooth kernels to purple wrinkled
kernels to yellow smooth kernels to yellow wrinkled kernels in a 9:3:3:1 ear of genetic corn from
Carolina Biological Supply and conclude that the only significant factor acting in this experiment
was chance.
Since both ears of corn had the ratio advertised by Carolina Biological Supply, we have
proven that the company is a reputable dealer of genetic corn.
Harvey 6
Literature Cited
celiac disease. (2009). In Encyclopædia Britannica. Retrieved October 15, 2009, from
Encyclopædia Britannica
Online: http://www.britannica.com/EBchecked/topic/101365/celiac-disease
genetics. (2009). In Encyclopædia Britannica. Retrieved October 15, 2009, from Encyclopædia
Britannica Online: http://www.britannica.com/EBchecked/topic/228936/genetics
Van heel, D.A. & West, J. (2006) Recent Advances in Coelaic Disease.GUT: An International
Journal of Gastroenterology and Hematology, 55, 1037-1046.