Synthesis-dependent strand annealing

Definition

Synthesis-dependent strand annealing (SDSA) is a DNA repair mechanism that involves the synthesis of new DNA to replace damaged or missing sections. This process is crucial during homologous recombination, where a template strand is used to accurately repair double-strand breaks in DNA, ensuring genomic stability and integrity. SDSA helps maintain genetic information by using complementary base pairing to guide the assembly of new strands.

5 Must Know Facts For Your Next Test

1. SDSA typically occurs after a double-strand break is detected and processed, allowing for the repair template to be used for accurate DNA synthesis.
2. Unlike other repair pathways like homologous recombination that may result in crossover events, SDSA usually does not lead to exchange of genetic material between homologous chromosomes.
3. The process of SDSA is characterized by the initial formation of a single-stranded DNA overhang that invades a homologous duplex, allowing synthesis to occur using the complementary strand.
4. SDSA is particularly important in preventing loss of genetic information because it relies on using the intact sister chromatid as a template during the repair process.
5. This mechanism plays a key role in maintaining genomic integrity during cell division and is vital for organisms' response to DNA damage.

Review Questions

• How does synthesis-dependent strand annealing contribute to the accuracy of DNA repair mechanisms?
  • Synthesis-dependent strand annealing contributes to the accuracy of DNA repair by utilizing a complementary template strand to guide new DNA synthesis. This process ensures that any damaged or missing sections of DNA are accurately replaced, preserving the original genetic sequence. By relying on the intact sister chromatid as a template, SDSA minimizes errors that could lead to mutations, thereby enhancing overall genomic stability.
• Discuss the differences between synthesis-dependent strand annealing and other homologous recombination pathways in terms of genetic exchange.
  • Synthesis-dependent strand annealing differs from other homologous recombination pathways primarily in its outcome regarding genetic exchange. While some homologous recombination processes can result in crossover events, leading to genetic variations between homologous chromosomes, SDSA typically avoids such exchanges. Instead, it focuses on accurately repairing the DNA using a homologous template without altering the genetic content, which is essential for maintaining genetic stability.
• Evaluate the implications of synthesis-dependent strand annealing on genomic integrity and cell cycle progression.
  • Synthesis-dependent strand annealing plays a critical role in maintaining genomic integrity by accurately repairing double-strand breaks through its template-guided synthesis mechanism. Its efficient functioning ensures that cells can progress through the cell cycle without accumulating mutations or chromosomal abnormalities that could lead to diseases like cancer. The effectiveness of SDSA in repairing DNA allows cells to respond appropriately to damage and sustain proper division and function, making it vital for organismal health and longevity.

Related terms

Homologous recombination: A type of genetic recombination where nucleotide sequences are exchanged between two similar or identical molecules of DNA, often involved in repairing DNA double-strand breaks.

Double-strand break: A severe form of DNA damage where both strands of the DNA double helix are broken, requiring effective repair mechanisms to prevent genomic instability.

Template strand: A strand of DNA that serves as a guide for synthesizing a new strand during DNA replication or repair processes.