Apentix/AP Biology/Unit 6: Gene Expression and Regulation/Question
AP Biologymediummcq1 pt

A Cas9-induced double-strand break in a coding exon is repaired by nonhomologous end joining (NHEJ). Which outcome is common at the repair site?

A.A small insertion or deletion that can disrupt the coding sequence
B.Exact restoration of the original sequence with no edit
C.Replacement of the exon with a donor template sequence
D.Conversion of neighboring genes into intronless copies

Explanation

Core Concept

NHEJ rejoins broken DNA ends without using a homologous template and often leaves small insertions or deletions. In a coding exon, an indel can disrupt the reading frame and knock out gene function, but not every NHEJ event produces a frameshift and the exact indel is not predictable.

Correct Answer

AA small insertion or deletion that can disrupt the coding sequence

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