Table 1. Pros and cons of CRISPRc and CRISPRi.

Feature	CRISPRc	CRISPRi
Average strength of observed phenotype	Strong	Medium
sgRNA design	Target sequence drives selection. Easy to identify efficient sgRNAs	Only a small number of sgRNAs give a desired phenotype. Identification of TSS necessary.
Tissue specificity	No specific concern	Differential promoter usage in specific tissues or context should be considered
False positives	Amplified genomic regions	Bidirectional promoters
False negatives	Exon skipping	Genes expressed from multiple promoters