Which statement best explains why, in a gene-targeted mutation, the DNA fragment is inserted at a specific locus?

Which statement best explains why, in a gene-targeted mutation, the DNA fragment is inserted at a specific locus?

• A. The DNA fragment is inserted through an electric current that allows it to be transported easily to the correct location.
• B. The DNA fragment is sized to replace the whole gene.
• C. The DNA fragment is flanked by DNA sequences that are identical to those found in the wild type.
• D. None of the above

Answer: (C)

In gene-targeted mutations, precise integration depends on homologous recombination guided by matching flanking sequences. The inserted DNA is bordered by two regions that are identical to the sequences at the target locus in the genome. These homologous arms align with the corresponding genomic DNA, allowing the cell’s repair machinery to swap in the new fragment exactly at that location. Delivery methods that move DNA into cells, like electroporation, don’t by themselves direct integration to a specific spot. Merely sizing the fragment to replace the whole gene doesn’t guarantee locus-specific insertion without those identical flanking regions. So the presence of identical sequences on both sides is what enables targeted, locus-specific insertion.

In gene-targeted mutations, precise integration depends on homologous recombination guided by matching flanking sequences. The inserted DNA is bordered by two regions that are identical to the sequences at the target locus in the genome. These homologous arms align with the corresponding genomic DNA, allowing the cell’s repair machinery to swap in the new fragment exactly at that location. Delivery methods that move DNA into cells, like electroporation, don’t by themselves direct integration to a specific spot. Merely sizing the fragment to replace the whole gene doesn’t guarantee locus-specific insertion without those identical flanking regions. So the presence of identical sequences on both sides is what enables targeted, locus-specific insertion.