Textbook Question
Explain how RNA participates in DNA replication.
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8. DNA Replication
Overview of DNA Replication
1:03 minutesProblem 14c
Textbook Question
Bacterial DNA polymerase I and DNA polymerase III perform different functions during DNA replication.
If a strain of E. coli acquired a mutation that inactivated DNA polymerase III function, would the cell be able to replicate its DNA? Why or why not?
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Understand the roles of DNA polymerase I and DNA polymerase III in DNA replication. DNA polymerase III is the primary enzyme responsible for synthesizing the new DNA strand by adding nucleotides to the growing chain during replication. DNA polymerase I, on the other hand, is involved in removing RNA primers and filling in the gaps with DNA nucleotides.
Consider the specific function of DNA polymerase III. It is highly processive and capable of synthesizing long stretches of DNA efficiently. Without this enzyme, the cell would lack the ability to perform the bulk of DNA synthesis during replication.
Analyze the consequences of inactivating DNA polymerase III. If this enzyme is non-functional, the cell would not be able to synthesize the leading strand or the Okazaki fragments on the lagging strand effectively, as no other polymerase in E. coli can fully compensate for its role.
Evaluate whether DNA polymerase I could compensate for the loss of DNA polymerase III. DNA polymerase I has a much lower processivity and is primarily involved in short patch repair, such as replacing RNA primers. It cannot perform the extensive DNA synthesis required for replication.
Conclude that the inactivation of DNA polymerase III would prevent the cell from replicating its DNA. This is because DNA polymerase III is essential for the elongation phase of replication, and no other enzyme in E. coli can substitute for its function in synthesizing long DNA strands.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Replication
DNA replication is the biological process by which a cell duplicates its DNA before cell division. This process involves unwinding the double helix and synthesizing new strands complementary to the original ones. It is essential for genetic continuity, ensuring that each daughter cell receives an identical copy of the DNA.
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Roles of DNA Polymerases
DNA polymerases are enzymes that synthesize DNA molecules from nucleotides, playing crucial roles in DNA replication. DNA polymerase III is the primary enzyme responsible for the bulk of DNA synthesis during replication, while DNA polymerase I is involved in removing RNA primers and filling in gaps with DNA. Each polymerase has distinct functions that are vital for accurate and efficient DNA replication.
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Mutations and Their Effects
A mutation is a change in the DNA sequence that can affect gene function and protein production. Inactivating a key enzyme like DNA polymerase III can severely disrupt DNA replication, as the cell may not be able to synthesize new DNA strands effectively. This can lead to incomplete replication and ultimately cell death if the mutation is not compensated by other mechanisms.
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