Correct Option: C. is hereditary Detailed Explanation: Sickle cell disease (SCD) is a genetic disorder that affects the shape and function of red blood cells. The disease is caused by a mutation in the hemoglobin gene, specifically the HBB gene located on chromosome 11. This mutation leads to the production of abnormal hemoglobin known as hemoglobin S (HbS). When oxygen levels are low, HbS causes red blood cells to deform into a sickle or crescent shape, which can lead to various health complications.

1. Hereditary Nature of Sickle Cell Disease:
2. Sickle cell disease is inherited in an autosomal recessive pattern. This means that a person must inherit two copies of the mutated gene (one from each parent) to develop the disease. If a person inherits only one copy of the mutated gene, they are considered a carrier (sickle cell trait) but typically do not exhibit symptoms of the disease.
3. This hereditary aspect is crucial because it explains why sickle cell disease can be prevalent in certain populations, particularly those of African, Mediterranean, Middle Eastern, and Indian descent. The carrier state (sickle cell trait) provides some protection against malaria, which is why the gene persists in these populations.
4. Why Other Options Are Incorrect:
5. A. Affects only black people: This statement is misleading. While sickle cell disease is more prevalent among individuals of African descent, it is not exclusive to them. It can also affect people from other ethnic backgrounds, including those from Mediterranean, Middle Eastern, and Indian populations. Therefore, this option is too narrow and does not accurately represent the global impact of the disease.
6. B. Kills the patient: This option is also misleading. While sickle cell disease can lead to severe complications and can shorten life expectancy, many individuals with the disease live into adulthood and can manage their symptoms with proper medical care. Advances in treatment and management have significantly improved the quality of life and longevity for many patients. Thus, stating that it "kills the patient" is an oversimplification and does not reflect the reality of living with the disease.
7. D. Affects blood cells: While this statement is true in that sickle cell disease does affect red blood cells, it is not the most defining characteristic of the disease. Many conditions affect blood cells, but the key aspect of sickle cell disease is its hereditary nature. Therefore, while this option is correct, it does not capture the essence of what makes sickle cell disease unique compared to other blood disorders.

Summary of Key Points:

• Sickle cell disease is a hereditary genetic disorder caused by a mutation in the hemoglobin gene.
• It is inherited in an autosomal recessive manner, requiring two copies of the mutated gene for the disease to manifest.
• The disease is not exclusive to any single ethnic group, although it is more common in certain populations.
• While it can lead to serious health complications, many individuals with sickle cell disease can live fulfilling lives with appropriate medical care.

Revision Summary:

• Sickle cell disease is hereditary and caused by a mutation in the hemoglobin gene.
• It follows an autosomal recessive inheritance pattern.
• The disease affects multiple ethnic groups, not just black individuals.
• Proper management can improve quality of life and longevity for those affected.