Sickle-cell anemia is caused by a mutation in the gene encoding hemoglobin, causing red blood cells to appear

a. half-moon shaped.
b. like discs.
c. spherical.
d. long and stringy.

The correct answer would be option A. half moon shaped.

Explanation:

Sickle-cell anemia is a genetic disorder in which normal blood cells become rigid or stick and look like a crescent moon or half moon shape. In sickle-cell anemia condition, there are not sufficient healthy red blood cells or RBCs to carry enough oxygen throughout the body.

In sickle-cell anemia, the mutation causes a single change in the amino acid of hemoglobin, the building block of oxygen-transport protein. The alpha and beta subunits are the two subunits of hemoglobin. In sickle cell anemia, the beta subunit has valine at position 6 instead of glutamic acid that is present in normal hemoglobin.

Thus, the correct answer is option A. half moon shaped.

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