Textbook Question
Predict the results of the experiment by Taylor, Woods, and Hughes if replication were
(a) conservative and
(b) dispersive.
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8. DNA Replication
Overview of DNA Replication
0:54 minutesProblem 9
Textbook Question
Which characteristics of DNA polymerase I raised doubts that its in vivo function is the synthesis of DNA leading to complete replication?
Verified step by step guidance1
Understand the role of DNA polymerase I: DNA polymerase I is an enzyme involved in DNA replication, primarily responsible for removing RNA primers and filling in the gaps with DNA nucleotides. However, its characteristics raised questions about its ability to perform complete DNA replication in vivo.
Examine the enzymatic activity of DNA polymerase I: DNA polymerase I has a relatively slow polymerization rate compared to other DNA polymerases, which suggests it may not be efficient enough to synthesize the entire genome during replication.
Consider the processivity of DNA polymerase I: Processivity refers to the ability of an enzyme to continuously synthesize DNA without dissociating from the template strand. DNA polymerase I has low processivity, meaning it frequently dissociates from the DNA template, which is not ideal for complete genome replication.
Analyze the abundance of DNA polymerase I: DNA polymerase I is present in relatively low quantities in cells compared to other polymerases, such as DNA polymerase III, which is the primary enzyme responsible for genome replication in prokaryotes.
Review experimental evidence: Studies have shown that DNA polymerase III, not DNA polymerase I, is the main enzyme responsible for the synthesis of the leading and lagging strands during DNA replication. DNA polymerase I primarily functions in repair and gap filling rather than complete replication.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Polymerase I Function
DNA Polymerase I is an enzyme involved in DNA replication and repair. It primarily functions to remove RNA primers from the lagging strand and replace them with DNA nucleotides. However, its relatively slow synthesis rate and lower processivity compared to other polymerases, such as DNA Polymerase III, raise questions about its efficiency in completing DNA replication in vivo.
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Processivity
Processivity refers to the ability of an enzyme to catalyze consecutive reactions without releasing its substrate. In the context of DNA polymerases, high processivity means that the enzyme can add many nucleotides to a growing DNA strand before detaching. DNA Polymerase I has lower processivity than DNA Polymerase III, which suggests it may not be the primary enzyme responsible for the rapid and continuous synthesis required during DNA replication.
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In Vivo vs. In Vitro
In vivo refers to processes occurring within a living organism, while in vitro refers to studies conducted outside of a living organism, typically in a controlled laboratory environment. The distinction is crucial when evaluating the function of enzymes like DNA Polymerase I, as its activity observed in vitro may not accurately reflect its role in vivo, leading to doubts about its primary function in DNA replication.
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