Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
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Chapter 28, Problem 2P
The Enzymatic Activities of DNA Polymerase I (a) What are the respective roles of the
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2a) There are two different DNA polymerase enzymes, DNA Polymerase I and DNA Polymerase III, that are active during prokaryotic DNA replication. Suppose you generated a mutant E. coli strain in which DNA Polymerase III was inactivated (all its enzymatic activities were non-functional) - assuming that all the other enzymes involved in replication remained fully functional, how would DNA replication in these mutant cells without DNA Pol III differ from DNA replication in normal E. coli? Briefly explain why you would expect to see that change/those changes in DNA replication in the mutant cells.
All known DNA polymerases catalyze synthesis only in the 5' → 3' direction. Nevertheless, during semiconservative DNA replication in the cell, they are able to catalyze the synthesis of both daughter chains, which would appear to require synthesis in the 3' → 5' direction on one strand. Explain the process that occurs in the cell that allows for synthesis of both daughter chains by DNA polymerase
The 3′ → 5′ exonuclease activity of Pol I excises only unpaired 3′-terminal nucleotides from DNA, whereas this enzyme’s pyrophosphorolysis activity removes only properly paired 3′-terminal nucleotides. Discuss the mechanistic signifi cance of this phenomenon in terms of the polymerase reaction.
Chapter 28 Solutions
Biochemistry
Ch. 28 - Semiconservative or Conservative DNA Replication...Ch. 28 - The Enzymatic Activities of DNA Polymerase I (a)...Ch. 28 - Multiple Replication Forks in E. coli I Assuming...Ch. 28 - Multiple Replication Forks in E. coli II On the...Ch. 28 - Molecules of DNA Polymerase III per Cell vs....Ch. 28 - Number of Okazaki Fragments in E. coli and Human...Ch. 28 - The Roles of Helicases and Gyrases How do DNA...Ch. 28 - Human Genome Replication Rate Assume DNA...Ch. 28 - Heteroduplex DNA Formation in Recombination From...Ch. 28 - Homologous Recombination, Heteroduplex DNA, and...
Ch. 28 - Prob. 11PCh. 28 - Prob. 12PCh. 28 - Chemical Mutagenesis of DNA Bases Show the...Ch. 28 - Prob. 14PCh. 28 - Recombination in Immunoglobulin Genes If...Ch. 28 - Helicase Unwinding of the E. coli Chromosome...Ch. 28 - Prob. 17PCh. 28 - Functional Consequences of Y-Family DNA Polymerase...Ch. 28 - Figure 28.11 depicts the eukaryotic cell cycle....Ch. 28 - Figure 28.41 gives some examples of recombination...Ch. 28 - Prob. 21PCh. 28 - Prob. 22P
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- 3aarrow_forwardWhat is the role of Mg2+ in this reaction?arrow_forwardHelicase Unwinding of the E. coli Chromosome Hexameric helicases, such as DnaB, the MCM proteins, and papilloma virus El helicase (illustrated in Figures 16.22 to 16.25), unwind DNA by passing one strand of the DNA duplex through the central pore, using a mechanism based on ATP-dependent binding interactions with the bases of that strand. The genome of E. coli K12 consists of 4,686,137 nucleotides. Assuming that DnaB functions like papilloma virus El helicase, from the information given in Chapter 16 on ATP-coupled DNA unwinding, calculate how many molecules of ATP would be needed to completely unwind the E. coli K 12 chromosome.arrow_forward
- Unlike linker DNA and deproteinized DNA, DNA segments wrapped around histone cores are relatively resistant to the hydrolytic actions of nucleases. Explain.arrow_forwardIn Polymerase Chain Reaction (PCR), the temperature is one of the most important parameters that could influence the efficiency of this technique. Each cycle of this reaction has its own specific temperature. For instance, the denaturation step possesses a temperature of 94 - 98 ℃ to ensure that the double stranded DNA is fully separated. (i) (ii) (iii) Why is the annealing temperature vital in this technique? Explain how will this temperature affects the efficiency of this reaction. Why is Hot Start PCR technique preferred by some researchers? If the primers you purchased possessed the following information. 5'-GGA AAC AGC TAT GAC CAT G-3' Calculate the melting temperature of this primer and estimate the annealing temperature of this primer.arrow_forwardAdenylate cydase, which synthesizes cyclic AMP from ATP, requires two metal ions, and the enzyme has the same constellation of amino acid residues in the active site as does DNA polymerase I. In what sense is the adenylate cyclase reaction similar to that of DNA polymerase, and in what sense is it different?arrow_forward
- Considering DNA sequencing by the Sanger method. It is correct to say that: * A)In the traditional method, radioactively “labeled” primers are used, allowing their visualization in autoradiography. B)In the automated method, a single reaction is performed containing the four “labeled” dideoxynucleotides, each with a different fluorophore. C)In both traditional and automated methods, the fragments are resolved and interpreted according to their ionization state. D)In the automated method, di-deoxynucleotides “labeled” with the same fluorophore are used, thus allowing their interpretation based on graphs of fluorescence emission. E)Sequencing reactions can use mRNA molecules, as long as they have a polyA tail.arrow_forwardDeoxyadenylate residues in DNA undergo deamination fairly readily, as do deoxycytidylate residues. (a) What is the product of dAMP deamination? (b) The deamination product is known to base-pair with A, C, or T. What would be the genetic consequences if this deaminated site in DNA were not repaired and if it paired with C on the next round of replication?arrow_forwardA mixture of four a-[*p]-labeled ribonucleoside triphosphates was added to permeabilized bacterial cells undergoing DNA replication in the presence of an RNA polymerase inhibitor, and incorporation into high-molecular- weight material was followed over time, as shown in the accompanying graph. After 10 minutes of incubation, a 1000-fold excess of unlabeled ribo- nucleoside triphosphates was added, with the results shown in the graph.arrow_forward
- A mixture of four a-[32P]–labeled ribonucleoside triphosphates was added to permeabilized bacterial cells undergoing DNA replication in the presence of an RNA polymerase inhibitor, and incorporation into high-molecular-weight material was followed over time, as shown in the accompanying graph. After 10 minutes of incubation, a 1000-fold excess of unlabeled ribonucleoside triphosphates was added, with the results shown in the graph. (a) Why was the excess of unlabeled rNTPs added?(b) How could you tell that radioactivity is being incorporated as ribonucleotides rather than as an alternative such as reduction to deoxyribonucleotides, followed by incorporation?(c) What does this experiment tell you about the process of DNA replication?arrow_forwardA mixture of four a-[32P]–labeled ribonucleoside triphosphates was added to permeabilized bacterial cells undergoing DNA replication in the presence of an RNA polymerase inhibitor, and incorporation into high-molecular-weight material was followed over time, as shown in the accompanying graph. After 10 minutes of incubation, a 1000-fold excess of unlabeled ribonucleoside triphosphates was added, with the results shown in the graph. Incorporation of radioactivity, cpm Excess (a) Why was the excess of unlabeled rNTPs added?(b) How could you tell that radioactivity is being incorporated as ribonucleotides rather than as an alternative such as reduction to deoxyribonucleotides, followed by incorporation?(c) What does this experiment tell you about the process of DNA replication?arrow_forwardIn the Inhibition of telomerase activity. Explain: (a) What is the process affected? (b) What is the Effect on the process? (c) Does it affect prokaryotes, eukaryotes or both?arrow_forward
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