Complications that arise at the replication fork because of dna- dependent dna polymerase catalyzed polymerization? How is this complication resolved
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Answer:
The need for accuracy probably explains why DNA replication occurs only in the 5′-to-3′ direction. If there were a DNA polymerase that added deoxyribonucleoside triphosphates in the 3′-to-5′ direction, the growing 5′-chain end, rather than the incoming mononucleotide, would carry the activating triphosphate.
In this case, the mistakes in polymerization could not be simply hydrolyzed away, because the bare 5′-chain end thus created would immediately terminate DNA synthesis.
It is therefore much easier to correct a mismatched base that has just been added to the 3′ end than one that has just been added to the 5′ end of a DNA chain.
Although the mechanism for DNA replication seems at first sight much more complex than the incorrect mechanism depicted earlier in Figure 5-7, it is much more accurate because all DNA synthesis occurs in the 5′-to-3′ direction.
An explanation for the 5′-to-3′ direction of DNA chain growth.An explanation for the 5′-to-3′ direction of DNA chain growth. Growth in the 5′-to-3′ direction, shown on the right, allows the chain to continue to be elongated when a mistake in polymerization has been removed by exonucleolytic
Despite these safeguards against DNA replication errors, DNA polymerases occasionally make mistakes. However, as we shall see later, cells have yet another chance to correct these errors by a process called strand-directed mismatch repair. Before discussing this mechanism, however, we describe the other types of proteins that function at the replication fork.
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