Download Hypercholesterolemia Questions KEY

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Hypercholesterolemia – Gel Electrophoresis Background Questions
Read pages 4-6 and look over the remainder of the packet to help you answer the following.
1. Describe the genetic mutation that affects LDL and explain why this would be problematic for a
person’s health?
Familial hypercholesterolemia is a dominant disease. When a person is affected by the disease
they are unable to efficiently remove LDL from circulation and it accumulates on the arterial walls.
2. Hypercholesterolemia is an autosomal dominant disease. What does this mean?
It is found on chromosome 19 and only one copy must be present for a person to have the
disease. Both homozygous dominant as well as heterozygous individuals will have the disease.
However, a person that is homozygous dominant will have a worse case of the disease.
3. What process amplifies genes? (Ie, this means to make many copies of.)
PCR (Polymerase Chain Reaction)
4. What are restriction enzymes?
Restriction enzymes are enzymes designed to find a specific sequence in DNA and then cut the
DNA at that point. They are responsible for creating DNA fragment polymorphisms, or chopped
up DNA where each piece is a different size.
5. What does RFLP stand for and what are they?
Restriction enzymes are first used to cut the DNA segment into pieces (fragments); each fragment will be
a different size based on where the DNA is cut. We call these fragments Restriction Fragment Length
Polymorphisms (RFLPs). These fragments will be separated on a gel based on their size and bands will
become visible. Each person’s DNA will produce unique bands since each person has unique DNA.
6. How can RFLPs show the presence of a mutation in a gene?
The pattern of bands produced on a gel electrophoresis will differ between healthy and diseased
individuals.
7. Is cholesterol essential? Explain.
Yes. It is needed as a main component of cell membranes. It is also very important in the brain
for learning and memory.
8. Where is cholesterol made within the body?
Liver.
9. Explain the difference between LDL and HDL.
LDL Cholesterol
~ Twice as big as HDL
~ Large amount of fat surrounded by
proteins
~ High lipid to protein ratio
~ Lower Density
~ Essential (ex. Need as part of cell
membranes), but accumulates in
arteries causing health issues when
present in too high of concentrations
~ Carries cholesterol from the liver to
the body
HDL Cholesterol
~ Half the size of LDL
~ Small amount of fat surrounded by
proteins
~ Low lipid to protein ratio
~ Higher Density
~ Essential for carrying LDL to the liver
when it can be removed from the body
~ Carries cholesterol from the body to
the liver
10. How do statins work to lower cholesterol?
Statins inhibit cholesterol synthesis in the liver.
11. Hypercholesterolemia is a dominant trait. Is there any advantage to being heterozygous for this
disease as opposed to homozygous dominant?
A person that is homozygous dominant had two copies of the diseased gene and will have a
more severe case of the disease.
12. What is Taq DNA polymerase?
An enzyme that is purified from a bacterium found in hot springs. It is capable of staying stable at
very high temperatures, whereas most enzymes denature when exposed to heat. It synthesizes
new copies of DNA during PCR.
13. Describe the following steps of PCR: (Third paragraph on page 6 and diagram on page 7 will help you here.)
a. Step 1: Denaturation
DNA complimentary strands are separated at 94oC, which is a very high temperature.
b. Step 2: Annealing
The sample is cooled to a temperature between 42oC and 65oC. This allows primers to be bind to
the target region (in this case the region where FH can be found) and make many copies of that
region.
c.
Step 3: Extension
The temperature is raised to 72oC and the Taq polymerase actually creates the new copies of the
gene so that there is enough present that it will be visible on a gel electrophoresis.
14. How many cycles typically occur during PCR?
25-40 cycles, which amplifies the targeted DNA exponentially
15. How can PCR and gel electrophoresis be used to diagnose someone with hypercholesterolemia?
Obtain DNA from chromosome 19 where the FH gene would be located. Perform PCR on the
unknown DNA and then match the results to that of healthy vs. diseased DNA.