Summary
Highlights
Stem cells are undifferentiated cells that can give rise to more cells of the same type and differentiate into other types of cells. In humans, a fertilized ovum forms an embryo, where cells are undifferentiated (embryonic stem cells) before they specialize into nerve or muscle cells through a process called differentiation.
Adult organisms also contain stem cells, for example, in bone marrow. Unlike embryonic stem cells, adult stem cells cannot differentiate into any type of cell; they are multipotent. Bone marrow stem cells differentiate to form blood cells like red blood cells, white blood cells, and platelets.
Stem cells are useful in medicine, particularly in bone marrow transplants to treat conditions like leukemia. The patient's bone marrow is destroyed, and then they receive a transplant of donor bone marrow. The stem cells in the transplanted marrow divide to form new bone marrow and differentiate into blood cells. Challenges include finding a compatible donor and the risk of virus transmission.
Another medical application is therapeutic cloning, where an embryo with the same genes as the patient is produced. Stem cells from this embryo can be transplanted without rejection by the patient's immune system, differentiating to replace damaged or non-functional cells. This technique could treat conditions like diabetes or paralysis, though it raises ethical and religious concerns.
Plants also have stem cells, found in meristem tissue at the tips of roots and buds. These meristematic stem cells can differentiate into any type of plant tissue throughout the plant's life. This property is used for rapid and inexpensive plant cloning, for example, to clone rare plants for conservation or to produce disease-resistant crop plants for farmers.