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Core Genetics & Mechanisms

Homology-Directed Repair (HDR)

A high-fidelity DNA repair mechanism that uses a homologous DNA sequence as a template to accurately fix double-strand breaks. Unlike NHEJ, HDR ensures precise integration or correction of genetic material.

Overview

Homology-directed repair (HDR) is a high-fidelity DNA repair mechanism that uses a homologous DNA sequence as a template to accurately fix double-strand breaks (DSBs). Unlike non-homologous end joining (NHEJ), HDR ensures precise integration or correction of genetic material, making it a cornerstone of advanced genome editing.

Frequently Asked Questions

When does HDR occur in the cell cycle?

HDR is activated during the S and G2 phases of the cell cycle, when a sister chromatid or donor DNA template is available for use as a repair template.

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Related Terms

Homologous Recombination

A precise DNA repair and genetic engineering mechanism that uses a homologous sequence as a template to exchange or replace genetic material. It allows for accurate correction or insertion of DNA sequences at defined genomic loci.

Non-Homologous End Joining (NHEJ)

A DNA double-strand break repair pathway that directly ligates broken DNA ends without requiring a homologous template. It is an efficient but error-prone mechanism that can introduce small insertions or deletions (indels).

Knockin (KI) Mouse Models

A genetically engineered mouse in which a specific DNA sequence—such as a gene, cDNA, mutation, reporter, or human ortholog—is inserted into a defined genomic locus to add or modify gene function.

Targeting Vector (Homology Arms)

A synthetic DNA construct designed to introduce specific genetic modifications into a genome through homologous recombination or HDR. It contains sequences known as homology arms that align precisely with the genomic target locus.

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