Explain What Will Happen To The Products Of Replication If Dna Polymerase 1 Is Absent?
Explain what will happen to the products of replication if DNA polymerase 1 is absent?
Explain what will happen to the products of replication if DNA polymerase 1 is absent?
DNA Polymerases
The polA gene encodes DNA polymerase I, which appears to be an auxiliary enzyme for DNA replication. Cells lacking this enzyme are viable, though those lacking the enzymes notable 5′ 3′ exonuclease activity are only partially viable until grown in high salt conditions. DNA polymerase I is crucial for cell survival after several forms of DNA injury, and its absence results in persistent single-stranded breaks that facilitate DNA recombination. DNA polymerase is a DNA polymerase enzyme. I appears to be an especially effective effector with DNA ligase in sealing single-stranded nicks, perhaps due to its ability to catalyze nick translation, in which the 5′-exonucleolytic removal of bases is linked to the synthesis activity. This property does not seem to be shared by any of the other DNA polymerases.
- Arthur Kornberg discovered DNA polymerase in E. coli lysates in 1956. Since this enzymes ability to faithfully replicate a DNA template established a biochemical basis for the mode of DNA replication first suggested by Watson and Crick, its isolation was a watershed moment in molecular biology. However, the first discovered DNA polymerase (now known as DNA polymerase I) is not the main enzyme involved in E. coli DNA replication. Instead, it is now clear that all prokaryotic and eukaryotic cells contain a diverse set of DNA polymerases, each of which plays a distinct role in DNA replication and repair.
- The isolation of a mutated strain of E. coli deficient in polymerase I showed the multiplicity of DNA polymerases for the first time. Specific bacterial colonies were isolated and tested to detect a mutant strain without polymerase I after E. coli cultures were treated with a chemical (a mutagen) that causes a high prevalence of mutations. A few thousand colonies were analyzed, and the desired mutant was isolated, which was almost completely deficient in polymerase I function.
- Surprisingly, the mutant bacteria developed normally, implying that polymerase I is not required for DNA replication. The mutant bacteria, on the other hand, were highly vulnerable to DNA-damaging agents (e.g., ultraviolet light), implying that polymerase I is involved mainly in the repair of DNA damage rather than in DNA replication per se.
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