Immature RBCs of mammals have

Options

A. No nucleus
B. Single beaded nucleus
C. Many nuclei
D. Single nucleus

Answer

**Step-by-Step Solution:**

1. **Understanding Immature RBCs**: Immature red blood cells (RBCs) in mammals are known as reticulocytes. They are the precursor cells that develop into mature red blood cells.

2. **Formation of Reticulocytes**: The process of forming red blood cells is called erythropoiesis. During this process, reticulocytes are formed and mature in the bone marrow.

3. **Circulation of Reticulocytes**: After their formation in the bone marrow, reticulocytes enter the bloodstream. They typically circulate for about one day before maturing into fully developed red blood cells.

4. **Nucleus in RBCs**: Both immature (reticulocytes) and mature RBCs in mammals do not have a nucleus. This absence of a nucleus is a key characteristic of these cells.

5. **Reason for Lack of Nucleus**: The lack of a nucleus in RBCs is advantageous because it allows for more space to carry hemoglobin, the molecule responsible for oxygen transport. If a nucleus were present, it would consume some of the oxygen that the cell is supposed to carry, reducing the efficiency of oxygen transport.

6. **Final Conclusion**: Therefore, the final answer to the question is that immature RBCs of mammals have no nucleus.