Ch. 10 - DNA Replication

Klug - Essentials of Genetics 10th Edition

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Klug 10th Edition

Ch. 10 - DNA Replication

Problema 9

Capitolo 10, Problema 9

Which characteristics of DNA polymerase I raised doubts that its in vivo function is the synthesis of DNA leading to complete replication?

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Understand the primary known activities of DNA polymerase I, which include its 5' to 3' polymerase activity, 3' to 5' exonuclease proofreading activity, and 5' to 3' exonuclease activity.

Recognize that DNA polymerase I has relatively low processivity, meaning it can add only a limited number of nucleotides before dissociating from the DNA template.

Note that DNA polymerase I's 5' to 3' exonuclease activity allows it to remove RNA primers but also limits its ability to synthesize long stretches of DNA continuously.

Consider that the enzyme's slower rate of DNA synthesis compared to other polymerases suggests it is not the main enzyme responsible for rapid and complete DNA replication.

Conclude that these characteristics—low processivity, presence of 5' to 3' exonuclease activity, and slower synthesis rate—raised doubts about DNA polymerase I being the primary enzyme for complete DNA replication in vivo.

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DNA Polymerase I Enzymatic Activities

DNA Polymerase I possesses multiple enzymatic functions, including 5' to 3' polymerase activity, 3' to 5' exonuclease proofreading, and 5' to 3' exonuclease activity. The presence of the 5' to 3' exonuclease allows it to remove RNA primers, but its relatively slow polymerization rate compared to other polymerases raised questions about its role in complete DNA replication.

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Percorso guidato

05:44

Repair Pathways

Processivity of DNA Polymerase I

Processivity refers to the number of nucleotides a polymerase can add before dissociating from the DNA template. DNA Polymerase I has low processivity, meaning it frequently dissociates, which is inefficient for synthesizing long DNA strands required for complete replication, suggesting it may not be the main enzyme for this task.

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Percorso guidato

08:39

mRNA Processing

Role of DNA Polymerase I in DNA Replication vs. Repair

While DNA Polymerase I can synthesize DNA, its primary in vivo role is believed to be removing RNA primers and filling short gaps during DNA repair and Okazaki fragment processing. This specialized function contrasts with the high-speed, high-processivity synthesis needed for complete genome replication, implicating other polymerases in that role.

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Percorso guidato

11:59

Steps to DNA Replication

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Domanda del libro di testo

Kornberg showed that nucleotides are added to the 3' end of each growing DNA strand. In what way does an exposed 3'-OH group participate in strand elongation?

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Domanda del libro di testo

How did Kornberg assess the fidelity of DNA polymerase I in copying a DNA template?

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What are the requirements for in vitro synthesis of DNA under the direction of DNA polymerase I?

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Predict the results of the experiment by Taylor, Woods, and Hughes if replication were