In a multicellular organism, nerve cells are different from muscle cells because -each cell type has a unique set of transcription factors and repressors, so it expresses a specific set of genes.
-each type of cell within a multicellular organism contains a different set of genes.
-random events within each cell regulate the expression of genes and result in different genes being expressed in different cells.
-cells gain and lose different genes during embryonic development, so each cell in an adult only has some genes from the original set.