<P> The oldest and most widely used expression systems are cell - based and may be defined as the `` combination of an expression vector , its cloned DNA , and the host for the vector that provide a context to allow foreign gene function in a host cell , that is , produce proteins at a high level '' . Overexpression is an abnormally and excessively high level of gene expression which produces a pronounced gene - related phenotype . </P>
<P> The oldest and most widely used expression systems are cell - based and may be defined as the `` combination of an expression vector , its cloned DNA , and the host for the vector that provide a context to allow foreign gene function in a host cell , that is , produce proteins at a high level '' . Overexpression is an abnormally and excessively high level of gene expression which produces a pronounced gene - related phenotype . </P>
protien export from the cell is an example of
protien export from the cell is an example of
gene expression
gene expression