Final answer:
Homology-directed repair in the CRISPR/Cas9 system requires a donor DNA template with sequence homology to the target site, following a double-stranded break induced by Cas9.
Step-by-step explanation:
In the CRISPR/Cas9 method of gene editing, homology-directed repair (HDR) takes place following the creation of a double-stranded break by the Cas9 enzyme. For HDR to occur, it is crucial to provide a template with sequence homology to the target DNA. This template will guide the repair of the DNA sequence, ensuring that alterations such as insertions or corrections are made with high fidelity.
The necessary components for HDR do not include sticky ends in Cas9's cuts or blunt ends, nor are they related to the presence of introns or the use of exonic splicing enhancers. Instead, the focus is on providing a donor DNA template with the desired sequence for precise gene editing. The introduction of this template takes advantage of the cell's native DNA repair system, facilitating a repair process that incorporates the designed changes into the genome.