Q: Genes control the identity of our cells and are the same in every cell, so why do we have different type of cells (nerves, muscles etc.)?
The right answer was: Each cell expresses genes differently
All our cells contain the same DNA. What makes a cell a nerve or a muscle is the differential expression of the genes through epigenetic mechanisms. Different combinations of epigenetic marks allow a gene to be switched on or off. Each cell type has its own set of epigenetic instructions to make cell identity. See the panel "What is Epigenetics" for more information.