Philosophy of Genetics: Development genes and stem cells
Development genes and stem cells
Human development is breathtaking in its complexity. After an egg is fertilized by a sperm, the cell starts to divide. Some of the earliest cells in the clump are known as embryonic stem cells because they can duplicate themselves endlessly, and change themselves (or differentiate) into any cell in the body by selectively switching off some of their genes.
Later, the cells become more specialized. The neural stem cells can only differentiate into neural cells of various kinds, and skin stem cells can only differentiate into skin cells (but not neural cells), even though the underlying genes in each cell are still the same (but selectively de-activated).
