Final answer:
Homologous recombination repair can occur during the S and G2 phases of the cell cycle to repair single-stranded and double-stranded DNA breaks, respectively. It is also employed during Meiosis I to ensure genetic diversity through the exchange of genetic material between homologous chromosomes.
Step-by-step explanation:
Homing in on Homologous Recombination Repair
Homologous recombination repair is an essential cellular process that ensures genetic stability by repairing DNA breaks. This mechanism can fix single-stranded or double-stranded breaks that occur due to damage or during replication.
The cell cycle stages in which homologous recombination repair is possible are primarily S and G2 phases. During the S phase, replication errors, single-stranded breaks, or nicks can occur, which recombination repairs by using the complementary DNA strand as a template. In the G2 phase, double-stranded breaks can be repaired before the cell enters mitosis, during which recombination uses sister chromatids as templates for repair.
Homologous recombination is also critical during meiosis, specifically in the prophase of Meiosis I, where it facilitates the exchange of genetic material between homologous chromosomes. This process not only repairs breaks but also contributes to genetic diversity.
At the molecular level, various proteins, such as the MRX/MRN complex, Sae2, and Sgs1, act in concert to mediate the repair. In addition, products of the BRCA1 and BRCA2 genes are involved in the repair of double-stranded DNA breaks within human cells, highlighting the process's significance in maintaining the integrity of our genome.