A group of scientists were using CRISPR to treat a mouse with cystic fibrosis, a disease caused by a defective Cl- channel protein called CFTR. The most common cause of cystic fibrosis in humans is the absence of a phenylalanine, an amino acid, in the CFTR protein, which prevents CFTR from achieving the correct 3-D structure. If the scientists wished to repair this mutation, how would they alter the mutated CFTR gene before using CRISPR to insert the DNA into the mice

they can insert the codon that encodes phenylalanine by CRISPR-Cas mediated homology-directed repair

Explanation:

The CRISPR (clustered regularly interspaced short palindromic repeats,)-Cas (CRISPR-associated protein) is a versatile technology for genome editing which has been developed by adapting a natural defense mechanism found in prokaryotic organisms. The CRISPR-Cas genome editing tool can be used to edit DNA sequences in eukaryotic genomes (for example, in human genomes) and thus restore gene function (in this case, the CFTR gene function). The system consists of a Cas protein that cleaves the DNA at specific genomic sites and a single guide RNA (sgRNA) that guides the Cas protein at specific genomic locations. CRISPR-Cas mediated homology-directed repair refers to the process where Cas cuts the DNA to triggers the homologous recombination (HR) DNA repair pathway, by which it is possible to insert new genetic sequences at specific genomic sites (in this case, the codon that encodes phenylalanine within the specific CFTR gene).

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