Q.31 In mammals, hematopoietic stem cells that give rise to different types of blood
cells are known as
(A) totipotent stem cells.
(B) pluripotent stem cells.
(C) myeloid progenitor cells.
(D) lymphoid progenitor cells.

Hematopoietic stem cells (HSCs) in mammals are multipotent stem cells capable of differentiating into all blood cell types from myeloid and lymphoid lineages. They reside primarily in the bone marrow and are essential for hematopoiesis, the process of blood cell formation. The correct answer to the multiple-choice question is none of the given options, as HSCs are neither totipotent, pluripotent, nor limited to just myeloid or lymphoid progenitors; however, standard biology references classify them as multipotent, making all options incorrect in strict terms.​

Option Analysis

Totipotent Stem Cells
Totipotent stem cells, like the zygote, can differentiate into all embryonic and extraembryonic tissues, including the placenta, but they do not exist in adult bone marrow or produce only blood cells. This option is incorrect for HSCs.​

Pluripotent Stem Cells
Pluripotent stem cells, such as embryonic stem cells, form all three germ layers (ectoderm, mesoderm, endoderm) but not extraembryonic tissues, and HSCs are more lineage-restricted to blood cells only. This option does not fit.​

Myeloid Progenitor Cells
Myeloid progenitors arise from HSCs and give rise to specific non-lymphoid blood cells like erythrocytes, platelets, and granulocytes, but not lymphoid cells. HSCs are upstream and broader, so this is incorrect.​

Lymphoid Progenitor Cells
Lymphoid progenitors derive from HSCs and produce lymphocytes (B cells, T cells, NK cells), but exclude myeloid lineages. This is too narrow for HSCs.​

Hematopoietic stem cells in mammals that give rise to different types of blood cells play a crucial role in maintaining blood production throughout life. These multipotent cells, often tested in exams like CSIR NET Life Sciences, differentiate into myeloid and lymphoid lineages under the process of hematopoiesis.​

Hematopoietic Stem Cells Defined

Hematopoietic stem cells (HSCs) reside in the bone marrow and possess self-renewal capacity while differentiating into all mature blood cells, including red blood cells, white blood cells, and platelets. Unlike totipotent or pluripotent cells, HSCs are multipotent, restricted to the hematopoietic system.​

Why Not Other Stem Cell Types?

• Totipotent stem cells form entire organisms, including extraembryonic tissues, irrelevant to blood cell production.​

• Pluripotent stem cells generate all body tissues from germ layers but lose potency early in development.​

• Myeloid and lymphoid progenitors are downstream from HSCs, committed to specific blood cell subsets.​

Relevance for CSIR NET

For competitive exams, recognize HSCs as multipotent; options like totipotent or pluripotent often appear as distractors due to potency confusion. Key markers include CD34+ and long-term repopulation assays.​