A: The target gene is preferably a single copy or no high similarity homologous gene. It means the functional redundancy gene of the target gene doesn’t exist. Otherwise, even there is a series of mutants of the target gene may not cause mutant phenotype. If you have to screen a gene with functional redundancy genes, these homologous genes should be screening. After hybridization phenotype and function could be analyzed. Besides, The GC content of the target gene should between 50%-70%.when a gene is amplified, the higher of the GC content, the better to screen.