Final answer:
When a nick on a DNA strand is detected, enzymes such as DNA ligase and proteins like RecA facilitate repair, either through simple sealing of the gap or via more complex homologous recombination processes to maintain genetic integrity.
Step-by-step explanation:
When a nick is detected on a DNA strand, biological processes for DNA repair are initiated. In the case of the lagging strand during DNA replication, the DNA ligase enzyme plays a pivotal role in sealing the nicks. These gaps are usually the sites where RNA primers were laid down to initiate synthesis of Okazaki fragments. The exonuclease activity of DNA polymerase I removes the RNA primers and fills in with DNA nucleotides. Once a DNA polymerase fills in these gaps, DNA ligase comes in to create phosphodiester bonds, effectively 'sealing' the nicks and completing the DNA strand.
For a broken replication fork resulting from a single strand nick, more complex repair mechanisms are involved. These include the use of exonucleases to trim back the DNA at the damaged site, and the use of the RecA protein to facilitate homologous recombination. This process involves the damaged DNA strand finding a homologous sequence on an undamaged sister strand, and using it as a template to repair itself, thus ensuring accurate repair without deletions or insertions.
In summary, once a nick is detected on a DNA strand, the repair process involves the collaboration of various enzymes and repair mechanisms to ensure that genetic information is preserved and errors are corrected. This showcases the intricate system of checks and balances present in cellular DNA replication and repair.