Drug-selection marker • Which drug-selection marker should I use? • Why isn't my drug-selection marker making my cells drug-resistant? Fluorescent protein • When should I use fluorescent proteins, luciferases or LacZ? • Which fluorescent protein should I use? • Why is my fluorescent protein so dim? Genome editing • What are the pros and cons of shRNA-mediated knockdown versus CRISPR- or TALEN-mediated knockout? • Should I use CRISPR or TALEN for genome editing? • Should I use single gRNA or dual gRNA for CRISPR-mediated knockout? • How is gRNA specificity score calculated? Protein expression • Why isn’t my bacterial expression vector expressing my recombinant protein? shRNA • How is shRNA knockdown score calculated? • Why isn't my shRNA knocking down my gene of interest? Virus packaging • Which viral vector should I use? • Can I transfect my viral vector directly into cells, or do I need to make virus first? • How is viral titer determined in VectorBuilder? • Why is the titer of my virus so low? Others • Should I use IRES or 2A (and which 2A) in my polycistronic expression cassette? • Why is the yield of my plasmid prep so low? • How to use piggyBac system in vitro and in vivo?