A question about cells and DNA - Is DNA specific for each cell?

No. All cells have the exact same DNA; whether they are brain cells, skin cells, or liver cells or any other cell type. The difference is how the DNA is expressed. Brain cells may turn on certain genes and turn off others; while liver cells will turn on other genes, but turn off others. This process is usually set in place during development using iRNA or hormones/protien. Certain iRNA or proteins may inhibit or prohibit expression of certain genes. Hope that helps.