Final answer:
The repair of DNA single strand damage involves nucleotide excision repair and the use of complementary base pairing for accuracy. RecA protein facilitates recombination with a homologous sequence to accurately repair damaged DNA. These processes maintain genetic integrity, which is vital for cell survival and species evolution.
Step-by-step explanation:
Understanding DNA Repair Mechanisms
When a single strand of DNA suffers damage, the cell employs various repair mechanisms to correct the defect using the undamaged complementary strand. Nucleotide excision repair is a process that involves removing the damaged nucleotide and then replacing it with a correct one based on the information on the undamaged strand. This repair relies on the complementary base pairing of DNA, where adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C).
During the repair of a single-stranded break, the RecA protein helps a single-stranded DNA filament search for homologous sequences on another DNA molecule. Once it finds a match, the damaged DNA strand can recombine and resume accurate replication. This is crucial for maintaining the genetic integrity and is a process conserved across all species.
In the event of a double-stranded break, proteins like Ku help align the DNA ends, and DNA ligase seals the joint, restoring the DNA's structure. Furthermore, during replication, each strand of DNA serves as a template for creating a new complementary strand, ensuring that each daughter cell inherits an accurate copy of the DNA sequence. This underlines the importance of DNA repair mechanisms in cell survival and species evolution.