Case Study: Sickle Cell Disease

You are the Doctor! Read the passage below and underline the important clue to this disease.

Patient description

In 1904 a student from the West Indies came to a Chicago physician, Dr. James Herrick, with a puzzling condition. Below is a summary of some of the observations Dr. Herrick made. Read the description and underline the information that may provide important clues that you think will help the doctor to diagnose the disease.

The patient reports feeling well most of the time. However, since he has been very young, there have been certain reoccurring symptoms. For instance, one day after swimming he became so tired after a few minutes that he could hardly move. He became short of breath and he complained of pain in his joints and muscles, especially the arms and legs. He complained of feeling weak during these times and required bed rest lasting a few weeks. These symptoms reoccurred repeatedly during his youth. He also had frequent fevers and infections.

The patient presented today with complaints of fatigue and soreness in the joints. Upon inspection the whites of his eyes had a yellowish tint. He complained of pain in the left abdominal area which was tender to the touch.

A family history reveals that he has two brothers and three sisters. None of them have this problem. His uncle and his grandmother used to have similar attacks. His grandmother died a young woman. His parents do not have this condition.

Your job is to learn more about this condition and to find out the cause of the symptoms. List the symptoms of this disease.

Some clues to help you. To learn more about this disease, you now study some clues to the cause of the disease. Follow the directions for each clue:

Clue A - Red Blood Cells: (See the Appendix for sketches) The job of red blood cells is to carry oxygen from the lungs to all the cells of the body. How is the shape of the patient’s red blood cells different from the shape of normal red blood cells? Describe the differences.

Clue B – Blood Vessels: Blood vessels are tubes that carry blood throughout the body. In order for blood to deliver oxygen to the cells, red blood cells must flow freely through the vessels. Look at the clues. (See Appendix) What effect will the patient’s red cells have on the movement of blood through the blood vessels? Describe.

Clue C – Hemoglobin: Hemoglobin is a protein found in red blood cells, It gives red blood cells their round shape and carries oxygen. Look at the clues. (See Appendix) Describe the difference between normal hemoglobin and the patient’s hemoglobin.

Clue A: Red Blood Cells (400X)

Normal Patient

Putting the Clues Together: Read the description of sickle-cell anemia below. Underline everything that you have discovered from the clues and the patient description.

Sickle cell anemia is a genetic disease that affects the hemoglobin molecule of red blood cells. The irregularly shaped blood cells lead to a cascade of symptoms. The sickled blood cells become hard and inflexible. Blood no longer flows freely through the capillaries and tends to clog causing pain and swelling. This condition results in a lower concentration of oxygen being delivered by the blood which in turn creates more sickling. The sickle-shaped red blood cells only last about ten days as opposed to the 120 day cycle of healthy red blood cells. The bone marrow cannot produce enough red blood cells to keep up with the demand, resulting in anemia. With an abnormally high amount of red blood cells breaking down, there is an excess of bilirubin present (bilirubin is a yellow pigment which results from the breakdown of hemoglobin). The liver usually removes bilirubin from the blood. If the liver cannot break bilirubin down gast enough, it builds up and jaundice results. Bilirubin can harden and cause gallstones.

A sickling episode, or crisis, can be brought on by infection, dehydration, overexertion, high altitude, chills or cold weather. Sometimes there is no apparent precipitating factor. Often people with sickle cell anemia are more susceptive to fevers and infection.

There is no cure for sickle-cell anemia. Hydration, bed rest, pain killers, and antibiotics are often prescribed.

Answer these questions:

1. What causes the sickle shape of red blood cells?
2. What happens to sickle cells when they try to move through the capillaries?
3. How long do sickle cells live? Healthy cells?
4. What causes anemia?
5. The word "jaundice" means a yellow color. Why does sickle cell cause people to turn yellow?
6. What can bring on a sickling episode?

Concept Map: Look at the concept map below. Fill in the sentences below with the correct terms. Not all terms will be used.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The disease called _______________________ is in the family. It is transmitted through____________________. Sickle cell anemia is caused by ____________. When there is low oxygen, abnormal hemoglobin forms __________________. Sickle cells lose their round shape. When they travel through the blood vessels they cause ______________. Sickle cells break easily which causes ______________.

 

 

 

 

 

How Can a Mutation in DNA Affect an Organism?

Sometimes the DNA code that makes up a gene has an error in it. This error is called a mutation. When the DNA contains an error, the mRNA it makes will copy that error. When the mRNA contains an error, it will code for incorrect amino acids and produce an incorrect protein.

Sickle-cell anemia is a disorder that gets its name from the sickle shape of the red blood cells. The sickled red blood cells are caused by a mutation in the hemoglobin of the person with the disorder. Hemoglobin is the main protein in red blood cells. Each hemoglobin molecule carries oxygen from the lungs to all other parts of the body.

Examine Table I in the Appendix. The two columns show a section of normal DNA and a section of DNA that has a mutation. This mutation is called sickle hemoglobin.

Fill in the mRNA for both kinds of DNA. Remember that A matches with U, T with A, C with G, and G with C.

Use Table II to fill in the amino acids for each DNA codon.

Put "Shape A" or "Shape B" in the row marked Shape of Blood Cells.

Answer these questions:

Look at the two DNA molecules in Table I. What base in the sickle hemoglobin is different from the normal hemoglobin? (Circle it)

What mRNA codon is different in sickle hemoglobin compared to normal hemoglobin?

What amino acid is different in sickle hemoglobin compared to normal hemoglobin?

What does this amino acid change do to the shape of red blood cells?

If you wanted to repair sickle hemoglobin, what change would you make?

What is this technique called?

Clue D in the Appendix has two drawings showing the amino acid sequence in normal and sickle hemoglobin. Indicate which one is normal and which one is sickle. How do you know?

Refer to the map of the following page showing parts of Asia and Africa. Map 1 shows areas where malaria occurs. Map 2 shows areas where sickle cell anemia occurs. Study these maps. What do they have in common? What conclusion can you make?

How do people get sickle-cell disease? What is the mode of inheritance?

 

 

Normal Patient

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Clue D: Amino Acid Sequences