I will knock out the instinsic gene first from the Jurkat cells or primary T cells later, and subsequently I want to introduce both haplotypes of this gene. In the lab we use viral vectors, eg gamma retroviruses or lentiviruses. Which is the best way to introduce both haplotypes in order to get 1:1 expression like in naturally occuring heterozygoty? I also use P2A after the gene to add also a marker of selection. Currently I have a construct with only one haplotype and the marker of selection.