Answer :
Pernicious anemia produces red blood cells that are large and vitamin B12 deficiency contributes to pernicious anemia.
Explanation:
When there is a lack of intrinsic factor, secreted in the parietal cells of the gastric mucosa or the stomach lining, vitamin B12 absorption from the stomach is affected.
Vitamin B12 is one of the key factors responsible for normal synthesis and maturation of fully functional red blood cells (RBCs).
The main function of the RBCs is to carry oxygen through hemoglobin to all parts of the body. In order to transport oxygen, the RBCs must be mature with normal shape (concave center and circular shape) and size.
When there is a lack of vitamin B12, the RBCs are not matured and immature, megaloblastic, large, irregularly-shaped red blood cells are formed and circulate in the blood. This also leads to macrocytosis of RBCs.
These cannot function as normal mature blood cells because of the irregular shape and cannot carry hemoglobin to transport oxygen.