Concept explainers
Answer the following questions concerning the accuracy of DNA polymerase during replication.
What general mechanism do DNA polymerases use to check the accuracy of
If a DNA replication error is detected by DNA polymerase, how is it corrected?
If a replication error escapes detection and correction, what kind of abnormality is most likely to exist at the site of replication error?
Identify two mechanisms that can correct the kind of abnormality resulting from the circumstances identified in part (c).
If the kind of abnormality identified in part (c) is not corrected before the next DNA replication cycle, what kind of mutation occurs?
DNA mismatch repair can accurately distinguish between the template strand and the newly replicated strand of a DNA duplex. What characteristic of DNA strands is used to make this distinction?
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Genetic Analysis: An Integrated Approach (2nd Edition)
- a) "Out of three E.coli DNA polymerases, DNA polymerases 3 has a high processivity and rate of polymerization and therefore better suited for replication of the genome" What is meant by processivity? how does the DNA polymerase 3 maintain high processivity? b) What is a replication fork ?. Give the protein/enzymes of a replication fork and describe their function?arrow_forwarda. Propose three different mutations to prevent initiation, elongation, and termination of bacterial DNA replication, respectively. Explain how/why each mutation would prevent its respective step. (Hint: mutations can be in genes that encode proteins or regulatory DNA sequences) b. In the early 1900s, Avery, MacLeod, and McCarty performed an experiment in bacterial cells to determine whether DNA, RNA, or protein functions as the 'transforming molecule' (i.e. the genetic material). In your own words, how did their experiment (depicted in the figure below) help to answer that question?arrow_forwardWhy is the replication of DNA referred to as a semiconservative process? What is the experimental evidence for the semiconservative nature of the process? What experimental results would you expect if replication of DNA were a conservative process?arrow_forward
- Indicate whether each of the following statements is true or false. If a statement is false, explain why it is false. A. The repair polymerase is the enzyme that proofreads the newly synthesized strands to ensure the accuracy of DNA replication. B. There is a single enzyme that degrades the RNA primers and lays down the corresponding DNA sequence behind it. C. DNA ligase is required to seal the sugar-phosphate backbone between all the DNA fragments on the lagging strand. D. The repair polymerase does not require the aid of the sliding clamp, because it is only synthesizing DNA over very short stretches. Answer the following questions about DNA replication. On a DNA strand that is being synthesized, which end is growing the 3' end, the 5' end, or both ends? Explain your answer. А. B. On a DNA strand that is being used as a template, where is the copying occurring relative to the replication origin-3' of the origin, 5', or both?arrow_forwardWhich of the followings statements are true about DNA polymerase? 1.) It can only go in one direction, meaning the lagging strand can't be synthesized continuously. 2.) It cannot start a DNA strand from scratch, so another enzyme is needed to create "primers" as a starting point. 3.) It cannot copy epigenetic marks (such as methyl groups) on its own; these must be "copied" onto the daughter DNA strand by other enzymes after DNA replication. 4.) All of the abovearrow_forwardWhat will be the outcome for any resulting protein from this this DNA segment  arrow_forward
- What factors promote the fidelity of replication during synthesis of the leading strand of DNA? prevention of mismatched nucleotides at the replication fork by topoisomerase Watson-Crick base pairing between the template and leading strand breaks that occur in the leading strand are repaired by DNA ligase removal of the RNA primers between Okazaki fragments by DNA polymerase I removal of wrongly inserted nucleotides by the 3'-exonuclease activity of DNA polymerase IIIarrow_forwardDefine DNA replication/synthesis and semiconservative replication. In addition, describe and/or define the role(s) of each of the following in the process of DNA replication/synthesis: DNA template strand, 5’ and 3’ ends, DNA helicase, DNA polymerase, single-strand binding proteins, topoisomerase, primase, Okazaki fragments, leading strand and lagging strand.arrow_forwardDiscuss the similarities and differences in the synthesis of DNA in the lagging and leading strands. What is the advantage of a primosome and a replisome as opposed to having all replication enzymes functioning independently of each other?arrow_forward
- What is/are the attributes that make nucleotide excision repair (NER) and base excision repair (BER) similar and/or different from each other? Select the correct response: The NER pathway is the only one that can remove DNA lesions in the strand regardless of their size which is followed by attaching the correct strand, then sealed by a DNA ligase. They both use the enzyme DNA glycosylases that recognizes the damaged DNA segments and proceed with repairing the faulty base in the strand. They differ NER only repairs purine bases while BER repairs pyrimidine bases. They both remove the damaged parts of the DNA where the BER pathway corrects only the identified damaged bases which are usually non-bulky lesions. The NER pathway, on the other hand, repairs the damage by removal of bulky DNA adducts which is a short-single stranded DNA segment. They both utilize the enzyme photolyase to reverse the damages created by the faulty section of the DNA. They both remove the damaged parts of the…arrow_forwardExplain in not more than 5 sentences. If deoxyribonucleotides that lack the 3’-OH groups are added during the replication process, what do you expect will occur?arrow_forwardDescribe three factors that account for the high fidelity of DNA replication.Discuss the quantitative contributions of each of the three.arrow_forward
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