The process by which a gene gets turned on in a cell to make RNA and proteins. Gene expression may be measured by looking at the RNA, or the protein made from the RNA, or what the protein does in a cell1.
Gene expression is the process the cell uses to produce the molecule it needs by reading the genetic code written in the DNA. To do this, the cell interprets the genetic code, and for each group of three letters it adds 1 of the 20 different amino acids that are the basic units needed to build proteins.. The information encoded in a gene is used to direct the assembly of a protein molecule. The cell reads the sequence of the gene in groups of three bases. Each group of three bases (codon) corresponds to one of 20 different amino acids used to build the protein24.
Genes encode proteins and proteins dictate cell function. Therefore, the thousands of genes expressed in a particular cell determine what that cell can do.