Essay Example on Comparing Zinc Finger Nucleases and Transcription Activator

The authors then went on to assess the type of mutations caused by ZFNs and TALENs Although both nucleases use FokI to generate double stranded breaks the resulting mutations repaired by NHEJ differ ZFNs were observed to produce smaller deletions accompanied by insertion of new bases showing a frequently occurring 4 base insertion TALENs on the other hand showed a larger deletion region and failed to show the recurrent 4 base pair insertions seen in ZFNs TALENs were also seen to favor simple deletions or deletions with insertions at their targets This data becomes essential when scientists decide which tool to use to generate random mutations in their targets In some targets it might be favorable to generate larger deletions accompanied by insertions using TALENs while in others smaller deletions may be preferred to avoid deleting surround sequences achievable by ZFNs The present article showed that two sets of TALENs can be simultaneously introduced into Drosophila thereby targeting two different regions in the genome this was done by introducing the mRNAs in the flies corresponding to the TALENs targeting two different targets So far the study compared ZFNs and TALENs with respect to NHEJ mediated repair following cleavage Next the authors delivered a donor oligonucleotide sequence to mediate homologous repair at the target site TALENs were seen to effectively incorporated the donor sequence and mutate the target with oligos homologous to both strands of the target sequence with results comparable to that of ZFNs Lastly the authors attempted to mutate genes for which successful mutants had not been isolated previously the targets were mutated in most cases except for two of the 17 TALEN pairs designed 

For one of these failed TALENs the authors explain that the long inter linker domain could be the attributing factor For two target genes Psf2 and Sld5 reducing the concentration of injected mRNAs for production of the TALEN in the fly eliminated lethality which was initially observed but resulted in infertile flies The same region targeted in ZFNs showed lethality at early stages of the fly again demonstrating the effectiveness of TALENs over ZFNs In conclusion TALENs were seen to be more effective than ZFNs in terms of having site specific activity with no to low off target activity and resulted in a higher number of desirable mutants TALENs are an important resource that might allow us to generate any mutant desired The present paper was successful in elucidating various aspects of TALENs design and usage such as inter linker domain size and mRNA dosage The various types of possible mutations at the targets were summarized as compared to ZFNs which will allow one to determine the desirable nuclease tool to use for genome editing Based on the current research results it would be interesting to apply the same study to other model organisms such as mice and determine if similar characteristics are seen