Here's why:
* Genes contain the instructions for building and maintaining an organism. These instructions dictate what proteins a cell will produce, and these proteins determine the cell's structure and function.
* During development, different genes are activated and deactivated in different cells. This selective gene expression leads to the production of different proteins, which in turn causes cells to specialize and take on distinct roles.
* For example: A muscle cell expresses genes that produce proteins responsible for muscle contraction, while a nerve cell expresses genes for proteins that help transmit signals.
While other factors like environment and cell-cell interactions play a role in differentiation, the fundamental control comes from the genes that are turned on and off in each cell.
