. After Okazaki's proposal of discontinuous DNA chain growth, therewas much controversy about whether both DNA strands are synthe-sized discontinuously, or only the lagging strand. Clearly, there is noneed for the leading strand to be synthesized in fragments, but manyworkers found that pulse-labeled DNA fragments hybridized toboth parental DNA strands. This finding indicated that bot.parental strands served as the template for synthesis of short DNAfragments. Propose an alternative mechanism by which leadingstrand replication could generate short fragments, and propose anexperimental test of your suggestion. (

DNA synthesis/replication occurs in 5' to 3' direction on both the strand. The leading strand…

Answered: . After Okazaki's proposal of…

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter28: Dna Metabolism: Replication, Recombination, And Repair

Section: Chapter Questions

Problem 10P: Homologous Recombination, Heteroduplex DNA, and Mismatch Repair Homologous recombination in E. coli...

See similar textbooks

Similar questions

Reiji and Tuneko Okazaki conducted a now classic experiment in1968 in which they discovered a population of short fragmentssynthesized during DNA replication. They introduced a shortpulse of 3H-thymidine into a culture of E. coli and extracted DNAfrom the cells at various intervals. In analyzing the DNA aftercentrifugation in denaturing gradients, they noticed that as theinterval between the time of 3H-thymidine introduction and thetime of centrifugation increased, the proportion of short strandsdecreased and more labeled DNA was found in larger strands.What would account for this observation?
Many of the gene products involved in DNA synthesis wereinitially defined by studying mutant E. coli strains that could notsynthesize DNA. Question: The dnaE gene encodes the a subunit of DNA polymeraseIII. What effect is expected from a mutation in this gene?How could the mutant strain be maintained?
Many of the gene products involved in DNA synthesis were initially defined by studying mutant E. coli strains that could not synthesize DNA. (a) The dnaE gene encodes the a subunit of DNA polymerase III. What effect is expected from a mutation in this gene? How could the mutant strain be maintained? (b) The dnaQ gene encodes the e subunit of DNA polymerase. What effect is expected from a mutation in this gene?
Homologous Recombination, Heteroduplex DNA, and Mismatch Repair Homologous recombination in E. coli leads to the formation of regions of heteroduplex DNA. By definition, such regions contain mismatched bases. Why doesnâ€™t the mismatch repair system of E. coli eliminate these mismatches?
Richard Boyce and Paul Howard-Flanders conducted an experimentthat provided biochemical evidence that thymine dimers areremoved from DNA by a DNA repair system. In their studies, bacterialDNA was radiolabeled so the amount of radioactivity reflectedthe amount of thymine dimers. The DNA was thensubjected to UV light, causing the formation of thymine dimers. When radioactivity was found in the soluble fraction, thymine dimershad been excised from the DNA by a DNA repair system.But when the radioactivity was in the insoluble fraction, the thyminedimers had been retained within the DNA. The following tableillustrates some of the experimental results involving a normalstrain of E. coli and a mutant strain that was very sensitive to killingby UV light: Explain the results found in this table. Why is the mutant strainsensitive to UV light?
During template-directed synthesis of a new DNA strand it can happen, if there are simple repeated sequences, that either the template strand or the strand being synthesized "slips" a short distance, and this can change the number of repeating sequence units in that stretch of repeated sequence. Which of the following processes involve such slippage? More than one answer is correct. Options: The increase in genomic copy number of a DNA transposon by transposition from a location behind a replication fork to a location ahead of the fork. Introduction of indels during DNA replication. The initial unwinding of the DNA duplex during replication by helicase. Increasing lengths of CAG trinucleotide repeats in the huntingtin gene giving rise to Huntington disease. Synthesis of primer by primase during DNA replication.
A certain mutant DNA polymerase is error-prone, tending to incorporate C opposite a template A. When such a DNA polymerase replicates a segment of DNA containing an A · T base pair, what will be the DNA composition in the daughter cells after (a) one and (b) two rounds of cell division? Assume that DNA repair does not occur.
DNA repair enzymes preferentially repair mis- matched bases on the newly synthesized DNA strand, using the old DNA strand as a template. If mismatches were instead repaired without regard for which strand served as template, would mismatch repair reduce repli- cation errors? Would such a mismatch repair system result in fewer mutations, more mutations, or the same number of mutations as there would have been without any repair at all? Explain your answers.
Using the numbered sites on the DNA double helix strands below, where would the DNA Primer ACTTGCGA bind to for DNA Amplification?
PolyADP-ribose polymerase (PARP) plays a keyrole in the repair of DNA single-strand breaks. In the pres-ence of the PARP inhibitor olaparib, single-strand breaksaccumulate. When a replication fork encounters a sin-gle-strand break, it converts it to a double-strand break,which in normal cells is then repaired by homologousrecombination. In cells defective for homologous recom-bination, however, inhibition of PARP triggers cell death.Patients who have only one functional copy of theBrca1 gene, which is required for homologous recombina-tion, are at much higher risk for cancer of the breast andovary. Cancers that arise in these tissues in these patientscan be treated successfully with olaparib. Explain how it isthat treatment with olaparib kills the cancer cells in thesepatients, but does not harm their normal cells.
In a typical microbiology laboratory, reasons for no bands from a gel of a polymerase chain reaction may bedue to errors relating to omission of ingredients in the reaction mix and absence of the target sequence inthe template DNA. Based on (i) primer problem and (ii) purity/potential contamination of the target sequence, explain the reason for non-appereance on bands.
(a) How fast does template DNA spin (expressed in revolutions per second) at an E. coli replication fork? (b) What is the velocity of movement (in micrometers per second) of DNA polymerase III holoenzyme relative tothe template?

SEE MORE QUESTIONS

Recommended textbooks for you

Biochemistry

ISBN:

9781305577206

Author:

Reginald H. Garrett, Charles M. Grisham

Publisher:

Cengage Learning

Biochemistry

ISBN:

9781305577206

Author:

Reginald H. Garrett, Charles M. Grisham

Publisher:

Cengage Learning

SEE MORE TEXTBOOKS