To make products from a gene, the information in the DNA is first copied, base for base, into a similar kind of information, into RNA . Once in the cytoplasm, the messenger RNA is translated using a different chemical language into the product of the gene, a protein . The sequence of the protein is defined by the original sequence of the DNA bases found in the gene. Mutations are changes in the DNA information. Mutations can cause protein products to be altered, missing from the cell, or present in incorrect amounts.
Genes make up only a subset of all the DNA in a cell.
Spacer DNA, which conveys no protein-coding information, makes the huge bulk of the DNA in our cells.