How cells become specialised, the types and uses of stem cells, the ethics of their use, and how gene expression is controlled.
All body cells contain the same genes, yet a nerve cell differs from a muscle cell. The difference comes from which genes are switched on — the control of gene expression.
Differentiation and gene expression
A stem cell is an undifferentiated cell that can divide and differentiate into specialised cells. During differentiation, only the genes needed for that cell type are expressed (transcribed and translated); others are switched off. So gene expression determines a cell's structure and function.
Control can occur at several points, but a key example is transcriptional control: transcription factors bind to DNA to switch genes on or off, so the right proteins are made in the right cells.
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