When we say a gene is expressing itself, what does "gene expression" mean in relation to protein synthesis?
When amino acids assemble, each particular order creates its own unique protein. As such, there are many different types of proteins that compose a cell, resulting in them producing numerous types of cells. They have their own proteins because different genes are expressed. Although cells essentially contain the same genes, cells can choose to express certain genes based on their function. As such, different gene expressions would entail different functions.