Table 3.
Comparison between the five most common genome editing tools
| Characteristics | ZNFs | CRE-LOXP | TALENs | FLP-FRT | CRISPR |
|---|---|---|---|---|---|
| DNA binding | Targeting particular DNA sequences with an engineered protein | Targeting particular DNA sequences with Cre recombinase enzyme | Targeting particular DNA sequences with an engineered protein | Targeting particular DNA sequences with FLP recombinase enzyme | Targeting particular DNA sequences with a short RNA sequence |
| Sensitivity/target | Less sensitive/protein-DNA interaction | Highly sensitive/recombinase-DNA interaction | Less sensitive/protein-DNA interaction | Highly sensitive/recombinase-DNA interaction | Highly sensitive/RNA–DNA interactions |
| Size of recognized target | 18–36 nucleotides | 38 nucleotides | 30–40 nucleotides | 20–35 nucleotides | 22 nucleotides |
| Ease of targeting multiple targets | Low | High | Low | High | High |
| Delivery | Easy | Variable (depends on the types of organism) | Difficult | Variable (depends on the types of organism) | Moderate |
| Design | Very complex | Simple | Complex | Simple | Simple |
| Nuclease-Monomer/Dimer | FokI-Dimer | Recombinase-Monomer/Dimer | FokI-Dimer | Recombinase-Monomer/Dimer | Cas/Monomer |
| Off-target effects | High | Low | Moderate | Lower than CRISPR | Low |
| Cytotoxicity | Variable to high | Variable | Low | Low | Low |
| Multiple targets | Difficult | Difficult | Difficult | Difficult | Easy |
| Cost/benefits | Expensive and time-consuming | Depends on the specific application and the resources available for genetic engineering experiments | Expensive and time-consuming | Depends on the specific application and the resources available for genetic engineering experiments | Cheap and less time needed |
| Mode of action | The target sequence should be surrounded by two sets of ZFN that must hybridize to each DNA strand | Cre recombinase recognizes the targeted DNA sequence and produce double strand breaks which then ligated back together in a different orientation | The target sequence must be surrounded by two sets of TALENs that must hybridize to each DNA strand | FLP recombinase recognizes the targeted DNA sequence and produce double strand breaks which then ligated back together in a different orientation | When gRNA is present, Cas may access the target DNA sequence and produce double strand breaks |
FLP flippase, ZNF zinc finger proteins, TALENs transcription activator-like effector nucleases, CRISPRs clustered regularly interspaced short palindromic repeats, FokI flavobacterium okeanokoites I, gRNA guide RNA, Cre cyclic recombinase, CRE-LOXP cyclic recombinase-locus of crossing (x) over P1, FLP-FRT flippase-flippase recognition targets