I want to know the methods which are robust to knockout the genes from the CHO genome. And to add the required gene as well which works for mammalian cells and gives best expression as well.
I would suggest you to use the CRISPR Cas9 system. It works very efficiently in CHO cells. By CRISPR Cas9 you can generate in/del mutations or replace entire gene. For more information and useful tips please follow the link: https://www.addgene.org/crispr/guide/.