Summary
Highlights
All cells in your body contain the same DNA, yet they differentiate into various types like nerve cells, blood cells, skin cells, and bone cells, each with a specific structure and function. This specialization is called differentiation.
You started as a single fertilized egg, a zygote, which divided to form a ball of identical, unspecialized embryonic stem cells. These cells have the ability to become any type of cell in the organism. Differentiation begins when the embryo is about eight cells big, as these stem cells specialize to form different tissues and organs.
Differentiation occurs because specific genes in the DNA are switched on or off, leading cells to produce different proteins. This unique combination of activated genes and resultant protein production dictates the cell's structure and function, causing them to look and operate differently.
Beyond the embryo, adult stem cells are found in infants, children, and adults. Unlike embryonic stem cells that can become any cell type, adult stem cells are multipotent; they can only form a few different types of cells, typically found within the tissue where they reside. They are crucial for repairing and replacing damaged tissues, such as the bone marrow stem cells that produce new blood cells.
Plants, unlike humans, retain the ability to use stem cells to form all types of specialized cells throughout their lives. Plant stem cells are located in meristems, found in the tips of growing roots and shoots. They can differentiate into any plant cell type, such as xylem or phloem. This capability allows for cloning plants from single meristem cells, a practice used for commercial propagation, like with bananas.
In summary, cell differentiation involves genes being switched on or off. Human embryonic stem cells can form all tissues and organs, while adult stem cells have limited differentiation capabilities mainly for repair. Plant stem cells, however, retain the ability to differentiate into all cell types throughout a plant's life.