Sickle Cell Anemia

1. Sickle Cell Anemia By Christine Turk

2. Normal Hemoglobin • Oxygen-carrying protein of RBCs • Causes red color of Red Blood Cells • Made of 4 polypeptide chains • 2 alpha and 2 beta chains • Creates a “doughnut” shaped RBC

3. Normal Hemoglobin

4. Sickle Cell Hemoglobin • single point mutation in hemoglobin beta chain (change in a single nucleotide pair) • Adenine to Thymine transversion (A to T) • Mutation replaces a glutamic acid with a valine at the 6th amino acid of the HBB • Changes the normal doughnut shape of the RBC to an odd sickle shaped cell

7. Sickle Shaped RBCs • Hemoglobin molecules aggregate and form fibers • These fibers cause the cell to sickle and become rigid and block capillaries • Sickled cells do not carry oxygen • Sickled cells are fragile and breakdown creating low RBC counts and anemia

9. Symptoms of Sickle Cell Anemia • Poor circulation and anemia deprive tissues of oxygen • Symptoms include tiredness, headaches, muscle cramps • Homozygous individuals experience poor growth, organ failure, and often a shortened lifespan (50% may die before the age of 20)

10. Affected Populations • This genetic trait is often associated with the African-American population in the U.S. • Is found in greater concentrations in populations originating where there is also a high mortality rate caused by a virulent form of malaria caused by the protist “Plasmodium falciparum”

11. RBCs containing sickle trait sickle when infected with the malaria parasite The parasite dies when the cell sickles and the individual is protected from a full-blown case of malaria

12. 25% HbN HbNNormal • Susceptible to Malaria • 50% HbN HbSCarrier • Does not demonstrate SCA symptoms • Not susceptible to Malaria • 25% HbS HbSSickle Cell • Not susceptible to Malaria • Demonstrates Sickle Cell Anemia