Homology-directed repair

Definition

Homology-directed repair (HDR) is a cellular process that repairs double-strand breaks (DSBs) in DNA by using a homologous sequence as a template. This method is crucial for maintaining genome stability and can be harnessed in genome editing techniques to introduce specific changes or corrections at the site of the break, allowing for precise modifications to the genetic material.

5 Must Know Facts For Your Next Test

1. HDR is considered a high-fidelity repair mechanism, as it can accurately restore or alter genetic sequences without introducing errors that can occur with other repair processes like non-homologous end joining (NHEJ).
2. This repair pathway is predominantly active during the S and G2 phases of the cell cycle when sister chromatids are available as templates.
3. Researchers can enhance HDR efficiency in cells by providing exogenous donor DNA templates that carry the desired genetic sequence for precise edits.
4. While HDR is beneficial for genome editing applications, its efficiency varies across different cell types and organisms, influencing the outcomes of experiments.
5. Understanding and manipulating HDR is crucial for developing gene therapies aimed at correcting genetic disorders by enabling specific and targeted interventions in affected individuals.

Review Questions

• How does homology-directed repair contribute to the accuracy of genome editing techniques?
  • Homology-directed repair enhances the accuracy of genome editing by utilizing a homologous sequence as a template to guide the repair of double-strand breaks. This precision allows researchers to introduce specific changes or corrections to the genetic material without causing unintended mutations. By ensuring that the edited sequence matches the desired template, HDR minimizes off-target effects, making it a preferred method for accurate genome engineering.
• Discuss the factors that influence the efficiency of homology-directed repair in different cell types.
  • The efficiency of homology-directed repair can vary widely among different cell types due to several factors, including the phase of the cell cycle, availability of template DNA, and the intrinsic repair machinery present within each cell. For instance, HDR is most effective during the S and G2 phases when sister chromatids are available as templates. Additionally, some cell types may have more robust mechanisms for recognizing and utilizing donor templates than others, impacting how successful HDR can be in achieving desired genomic alterations.
• Evaluate the potential implications of manipulating homology-directed repair pathways for therapeutic applications in gene therapy.
  • Manipulating homology-directed repair pathways holds significant potential for advancing gene therapy approaches aimed at correcting genetic disorders. By enhancing HDR efficiency through various strategies, such as providing optimized donor templates or employing small molecules that promote HDR over NHEJ, researchers can achieve more precise genomic corrections. This ability could lead to effective treatments for diseases caused by single-gene mutations, ultimately transforming therapeutic outcomes and offering hope for patients with previously untreatable conditions.

Related terms

Double-strand break: A type of DNA damage where both strands of the DNA molecule are severed, often leading to cell death if not repaired.

CRISPR-Cas9:

A revolutionary genome editing tool that utilizes a guide RNA and the Cas9 enzyme to create targeted double-strand breaks in DNA, facilitating HDR and other repair mechanisms.

Template DNA: A DNA sequence used as a reference during the repair process, guiding the incorporation of new genetic information into the genome through HDR.