Vitamin B12 deficiency impairs DNA synthesis, primarily manifesting as which hematological condition?

💡 Explanation:

Vitamin B12 (cobalamin) is a crucial cofactor for DNA synthesis. A deficiency leads to defective DNA production, which disproportionately affects rapidly dividing cells, such as red blood cell precursors in the bone marrow. This results in the formation of abnormally large, immature red blood cells (megaloblasts), a condition known as megaloblastic anemia. Iron-deficiency anemia is microcytic, hemolytic anemia is due to RBC destruction, and aplastic anemia is total bone marrow failure.