The processes that give rise to DNA damage and are relevant for DNA repair are c
ID: 147528 • Letter: T
Question
The processes that give rise to DNA damage and are relevant for DNA repair are constrained by the structural biochemistry of DNA and the molecular mechanisms involved in DNA repair Comprehensively review these related subjects in an organized fashion that illustrates the underlying biochemical features. Your answer should stress mechanistic details and components that are common to both damage/repair biochemistry and the processes and machinery of replication. Be sure to address both eukaryotic and prokaryotic processes and their regulation. Finally, why does it make sense that DNA repair and replication should share common features from evolutionary and mechanistic standpoints?Explanation / Answer
Although genetic variation is important for evolution, the survival of the individual demands genetic stability also. Maintaining genetic stability requires not only an extreme accurate mechanism for replicating DNA, but also mechanisms for repairing the many accidental lesions that occur continually in DNA. Most such spontaneous change in DANA are temporary because they are immediately corrected by a set of processes that are collectively called as DNA repair.
DNA repair is possible because DNA molecule consists of ttwo complementary strands. DNA damage in one strand can be removed and accurately replaced by using complementary strand as a template.
Molecular mechanisms involved in ssDNA repair:
Molecular mechanism for dsDNA:
Enzymatic machinery for this repair process is nearly identical to the machinery responsible for chromosonsl crossover during meiosis.
The 3' to 5' Proof-Reading Exonuclease
The 3' to 5' proof-reading exonuclease works by scanning along directly behind as the DNA polymerase adds new nucleotides to the growing strand. If the last nucleotide added is mismatched, then the entire replication holoenzyme backs up, removes the last incorrect base, and attempts to add the correct base again. The enzyme is "3' to 5'" because it scans in the opposite direction of DNA replication, which we learned must always be 5' to 3'. The mechanism of the proof-reading system offers an explanation as to why DNA replication must occur in this direction
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