Abstract: A method of screening multiply transformed/transfected cells to identify those cells expressing at least two peptides or proteins of interest. The method comprising: 1. Simultaneously or sequentially transforming a cell with at least two different expression cassettes in which the gene of interest is linked via an IRES to a fluorescent marker gene. Each marker gene is different. 2. Providing conditions in which expression of the genes will occur. 3. Identifying cells expressing proteins by detecting the different fluorescent signals.

Abstract: The present invention pertains to genetic screening methods and related cells and genetic constructs. In particular, the invention relates to a method of screening cells for an alteration, typically an amplification, in the copy number of a nucleic acid of interest using an amplifiable nucleic acid linked to a reporter nucleic acid; a method of screening cells for increased expression of a polypeptide of interest derived from the nucleic acid of interest; and related cells and genetic constructs. The method allows for high throughput screening of recombinant cells expressing a polypeptide or protein of interest and, in particular, for screening of cells expressing the polypeptide or protein of interest at elevated levels.