Person having heterozygous sickle cell trait is protected from infection of ?
**Core Concept**
The question is based on the concept of **sickle cell trait** and its relationship with **malaria**. Individuals with sickle cell trait have one normal and one sickle cell allele, which provides some protection against certain infections.
**Why the Correct Answer is Right**
The correct answer is related to the fact that **heterozygous sickle cell trait** offers protection against **Plasmodium falciparum malaria**. This is because the sickle cell allele interferes with the lifecycle of the parasite within red blood cells, reducing the severity of the disease. The exact mechanism involves the **sickle hemoglobin** (HbS) polymerizing under low oxygen conditions, which affects the parasite's ability to survive and multiply.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while sickle cell trait may have other benefits, the specific protection is not against all infections.
**Option B:** Incorrect as the question is about a specific protection offered by sickle cell trait, not about increasing susceptibility.
**Option C:** Incorrect because the protection is specific to a particular type of infection, not a broad range of diseases.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember that **sickle cell trait** is different from **sickle cell disease** and offers a unique advantage in areas where **malaria** is prevalent. This is a key point in understanding the evolutionary advantage of the sickle cell allele in certain populations.
**Correct Answer:** Correct Answer: D. Malaria.