The central element for all living things is carbon, which is why you might often hear the phrase "carbon-based" lifeforms. Another term is often "organic matter"
Are you talking about the esophagus?
The DNA is stored in the nucleus of the cell. Different genes are active in different kinds of cells. Most living things are composed of different kinds of cells specialized to perform different functions. A liver cell, for example, does not have the same biochemical duties as a nerve cell.
It would be called a mutation
