Download Project 8.2.7 Mystery Disease Part 2: Genetic Testing Introduction

Project 8.2.7 Mystery Disease Part 2: Genetic
Testing
Introduction
At the conclusion of the previous assignment, you determined that the patient, Joe
Bloggs, should be tested for Huntington’s disease based on family history and the
patient’s symptoms. Huntington’s disease is an inherited disease that is caused by a
mutation in the DNA of the affected person. DNA, or deoxyribonucleic acid, is a
molecule located in the nucleus of the cell that determines the structure of proteins
produced in the cell. This genetic information is inherited, or passed from parent to
child, with half of the child’s DNA coming from each parent. A person with
Huntington’s disease has a mutation or change in their DNA that causes a mutation
in the resulting protein.
To confirm a diagnosis of Huntington’s disease, a genetic test is performed that
identifies if the person has the mutation in his or her DNA. DNA must be isolated
from the rest of the cell before genetic testing can occur. This chemical process
involves collecting the cells, dissolving the cell membrane, and gathering the DNA
molecules together. Once the DNA has been isolated, it can undergo a variety of
different genetic tests.
In this project you will learn more about Huntington’s disease and investigate how
DNA is isolated for genetic testing by collecting your cheek cells, isolating DNA, and
creating a necklace with your isolated DNA.
Equipment
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Laboratory Journal
Pencil
Computer with Internet access
Medical History Form from 8.2.6
Carolina DNA Necklace Kit
 Small plastic cup with 2 mL of sport drink
 15-mL tube
 Plastic pipet
 Pendant tube
 Piece of embroidery thread
 Lysis solution
 Ice cold 70% ethanol
Safety goggles
Latex or nitrile gloves
Permanent marker
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Procedure
What is Huntington’s Disease?
1. As a class or individually, watch the video titled “What is Huntington’s Disease?”
at http://hopes.stanford.edu.
2. Visit the page on the HOPES website titled “Bryan’s Dad has Huntington’s
Disease” and read through Part I. https://www.stanford.edu/group/hopes/cgibin/wordpress/2010/07/bryans-dad-has-huntingtons-disease/
As you read, answer conclusion questions 1-8.
3. As time allows, investigate Huntington’s disease on the HOPES website.
How is DNA isolated?
DNA is often described as the “code of life” because it determines an organism’s
characteristics and is passed from one generation to the next. DNA is located in almost
every cell of your body. The length of DNA is about 100,000 times as long as the cell
itself. However, it fits into the nucleus, which takes up only about 10% of the cell’s
volume by folding around proteins and compacting into chromosomes.
Answer the questions below as your teacher reviews the structure of DNA.
1. What are the base pairs?
2. What molecule is encoded by genes?
3. Describe the basic structure of DNA.
4. What is a histone?
5. How many chromosomes do human beings have?
6. Label the image below:
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7. Describe the three steps involved in precipitating and isolating DNA from cheek
cells as your teacher continues the presentation.
a. Collect cheek cells
b. Cell lysis
c. DNA precipitation
8. What is the importance of DNA extraction?
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Follow the directions below to extract and isolate the DNA from your cheek cells.
4. Obtain the DNA Necklace Instructions handout and workstation supplies.
5. Follow the directions on the DNA Necklace Instruction handout to complete the
experiment.
6. After you have created your DNA necklace, either take a photo of the DNA in the
vial or draw a picture of your observations.
7. While you are waiting for the DNA to precipitate out of the lysate solution, answer
conclusion questions 9-11 from the inherited diseases presentation.
8. Answer remaining conclusion questions.
Conclusion
1. According to the story, what symptoms typical of HD did Bryan’s dad display?
2. How old is Bryan’s dad now and how old was he when his mother died from
Huntington’s disease?
3. Why are the chances of inheriting Huntington’s disease like flipping a coin?
4. What cells are damaged in Huntington’s disease and where in the brain are they
located?
5. What gene on Bryan’s dad’s DNA is mutated?
6. Would you expect Bryan’s dad to have more or less than 40 codons of CAG in
his Huntington gene? Why?
7. How does the huntingtin protein damage cells?
8. How is Huntington’s disease confirmed?
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9. Explain how a recessive genetic disease is inherited.
10. Explain how a dominant genetic disease is inherited.
11. Is Huntington’s disease a recessive or dominant genetic disease?
12. Were you able to see the double helix structure of the DNA that condensed in the
vial? Why or why not?
13. What percent chance does the teenage daughter of the patient have of getting
Huntington’s disease?
14. Would you recommend that the daughter be tested for the HD mutation? Why or
why not?
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