Single-strand breaks

Definition

Single-strand breaks are disruptions that occur in one of the two strands of the DNA helix, leading to a break in the sugar-phosphate backbone. These breaks can arise from various sources, including ionizing radiation and chemical agents. Understanding single-strand breaks is crucial, as they can be repaired through specific cellular mechanisms, and their consequences can lead to further DNA damage or genomic instability if not addressed promptly.

5 Must Know Facts For Your Next Test

1. Single-strand breaks are considered less severe than double-strand breaks, but they still pose significant risks for cellular function and genetic integrity if not repaired.
2. Cells utilize several repair pathways for single-strand breaks, including base excision repair and nucleotide excision repair, which help restore the DNA structure.
3. Persistent single-strand breaks can lead to replication stress during cell division, increasing the likelihood of double-strand breaks and other forms of DNA damage.
4. The accumulation of unrepaired single-strand breaks may contribute to various diseases, including cancer, as they can result in mutations or chromosomal aberrations.
5. Single-strand breaks can also affect gene expression by altering the normal transcription processes, potentially leading to dysfunctional protein synthesis.

Review Questions

• How do single-strand breaks differ from double-strand breaks in terms of their impact on DNA repair mechanisms?
  • Single-strand breaks involve a disruption in only one strand of the DNA helix and are typically repaired through less complex mechanisms such as base excision repair. In contrast, double-strand breaks present a more challenging scenario, as both strands are broken, requiring more intricate repair pathways like homologous recombination or non-homologous end joining. The difference in complexity affects how cells respond to each type of damage and the potential consequences for genomic stability.
• Discuss the potential consequences of unrepaired single-strand breaks on cellular function and genomic integrity.
  • If single-strand breaks remain unrepaired, they can lead to replication stress during cell division as the DNA polymerase encounters these interruptions while replicating DNA. This may increase the likelihood of further damage, such as double-strand breaks, which are more detrimental. Over time, the accumulation of unrepaired single-strand breaks can result in genomic instability, contributing to mutagenesis and potentially leading to conditions like cancer.
• Evaluate the role of single-strand breaks in the context of therapeutic strategies aimed at treating cancer through targeting DNA repair pathways.
  • In cancer therapy, exploiting the presence of single-strand breaks can be a strategic approach to sensitize cancer cells to treatment. By inhibiting specific DNA repair pathways that handle single-strand breaks, such as PARP inhibitors, clinicians can effectively increase genomic instability within cancer cells. This strategy takes advantage of the fact that many cancer cells already have compromised DNA repair mechanisms. Consequently, this makes them more susceptible to further damage and death when faced with therapies that induce additional DNA breaks.

Related terms

DNA Repair:

The collection of processes by which a cell identifies and corrects damage to its DNA molecules, ensuring the integrity of the genetic material.

Double-Strand Breaks: A more severe form of DNA damage where both strands of the DNA helix are broken, often leading to more complex repair challenges and higher risks of mutations.

Genomic Instability:

A condition where the genome is prone to mutations, chromosomal rearrangements, and other forms of genetic abnormalities, often linked to inadequate DNA repair mechanisms.