MCQ Detailed View

Sickle cell anemia is a hereditary genetic disorder of the blood that affects the structure and function of red blood cells. Normally, red blood cells are round and flexible, allowing them to move easily through blood vessels. In sickle cell anemia, a mutation occurs in the HBB gene on chromosome 11, which encodes the protein hemoglobin. Specifically, this mutation causes the production of an abnormal type of hemoglobin known as hemoglobin S.

When hemoglobin S is exposed to low oxygen levels, it tends to clump together and distort the red blood cells into a rigid, crescent or “sickle” shape. These sickle-shaped cells have several harmful consequences:

1. 
   

   Shorter Lifespan – Normal red blood cells live about 120 days, but sickled cells die within 10–20 days, leading to a shortage of red blood cells (anemia).

   
   


2. 
   

   Blockage in Blood Vessels – Due to their irregular shape and stiffness, sickled cells can block small blood vessels, restricting oxygen flow to tissues and causing severe pain episodes, called sickle cell crises.

   
   


3. 
   

   Organ Damage – Chronic oxygen deprivation and poor circulation can damage organs such as the spleen, liver, kidneys, heart, and brain.

   
   


4. 
   

   Increased Infections – The spleen is often damaged in sickle cell patients, making them more vulnerable to bacterial infections.

   
   

Sickle cell anemia is inherited in an autosomal recessive pattern. This means a person must inherit two defective copies of the HBB gene (one from each parent) to develop the disease. Those who inherit only one defective gene are carriers, known as having the “sickle cell trait,” and usually do not experience severe symptoms but can pass the gene to their children.

There is currently no universal cure, though treatments such as blood transfusions, bone marrow transplants, and medications like hydroxyurea help manage the condition and reduce complications.

In conclusion, sickle cell anemia is not caused by viruses, bacteria, or vitamin deficiencies—it is strictly a genetic disorder. This classification makes it an important topic under Biology MCQs, particularly in genetics and human health.