Which of the following best describes sickle-cell anemia? O Caused by environmental factors that an individual was exposed to during pregnancy. O A hereditary genetic mutation that causes a resistance to malaria. O An inherited disorder that increases the risk of contracting malaria from mosquitos. O A genetic mutation that is inherited from a dominant allele of one parent.
The Correct Answer and Explanation is:
The correct answer is:
A hereditary genetic mutation that causes a resistance to malaria.
Explanation:
Sickle-cell anemia is a hereditary genetic disorder caused by a mutation in the hemoglobin gene, which affects the shape of red blood cells. Normally, red blood cells are round and flexible, allowing them to move smoothly through blood vessels. However, in individuals with sickle-cell anemia, the mutation causes hemoglobin to form abnormally, making red blood cells rigid and crescent-shaped (or “sickle-shaped”). These sickle-shaped cells can clog blood vessels, leading to pain, organ damage, and other complications.
The mutation that causes sickle-cell anemia is located in the HBB gene on chromosome 11. It is inherited in an autosomal recessive manner, meaning an individual must inherit two copies of the mutated gene—one from each parent—to have the disease. However, individuals who inherit only one copy of the mutated gene (heterozygotes) do not have sickle-cell anemia but are carriers of the trait, a condition known as sickle-cell trait.
Interestingly, people with sickle-cell trait (heterozygous individuals) have a higher resistance to malaria, a deadly disease caused by Plasmodium parasites transmitted through mosquito bites. The malaria parasite is less able to survive in sickle-shaped red blood cells, providing a survival advantage in malaria-endemic areas. This is why sickle-cell anemia is most commonly found in populations from regions where malaria is prevalent, such as parts of sub-Saharan Africa, the Mediterranean, and parts of India and the Middle East.
While sickle-cell anemia confers resistance to malaria, it also poses serious health risks for those who inherit two mutated copies of the gene, including painful sickle-cell crises, organ damage, and other complications.
