what if red blood cells get nucleus?

Answer 1

Red blood cells are made in the bone marrow. They start out with a nucleus, like other cells, but when they fill up with hemoglobin the nucleus is squished smaller and smaller until it disappears. With no nucleus, red blood cells are fragile and live only about 120 days. In your body, about 2 million red blood cells die per second! But your bone marrow produces new ones just as fast.

Answer 2

Red blood cells strat out in the marrow as nucleated cells, However, by the time they are released into the bloodstream, they have normally lost their nuclei. The presence of nucleated red cells in the peripheral circulation suggests that active formation of formation of erythrocytes is occuring in reponse to something like anemia from blood loss or lead poisoning. There are also erythrocytic leukemias in which primitive nucleated precursor-like cells are present in the blood. This discussion is all pertaining to humans.

For birds, nucleated red blood cells are normal!