Yes, all cells in a multicellular organism have the same set of genes. However, different cells express different genes, meaning they activate different genes to produce different proteins. This is what allows cells to specialize and perform different functions.

Here's why:

* DNA is the blueprint: All cells in an organism contain the same DNA, which is the blueprint for building and maintaining the organism.

* Gene expression: Genes are sections of DNA that code for proteins. Each cell only expresses a subset of its genes, based on its role in the organism.

* Cellular specialization: This selective gene expression leads to the development of different cell types, each with specific functions. For example, a muscle cell expresses genes for proteins involved in contraction, while a nerve cell expresses genes for proteins involved in transmitting signals.

So, while all cells have the same genes, they activate different genes to become specialized and perform different functions.