Recombinant DNA and Biotechnology (1B) Practice Test

A study uses CRISPR-Cas9 to knock out a DNA repair gene in a human cell line to test sensitivity to a chemotherapy agent. Two clonal lines are isolated: Clone X and Clone Y. Sequencing of the target locus shows that Clone X has a frameshift insertion near the start codon, while Clone Y has an in-frame 3-bp deletion. After drug treatment, Clone X shows markedly reduced survival compared with the parental line; Clone Y shows survival similar to parental.

Based on the scenario, which conclusion is most supported by the use of CRISPR-Cas9 editing in this context?

A researcher uses CRISPR-Cas9 to edit a single base in a gene associated with an inherited disease, aiming to restore the wild-type sequence in patient-derived cells. After editing, sequencing shows both corrected alleles and unedited alleles in the population.

Which result would be expected if the edited cells are not clonally isolated before analysis?