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Mutations in the dnaA gene of E. coli are lethal. Therefore, we can only study such mutations if we are able to generate conditional mutations (mutations whose effect takes place only in certain conditions). One type of conditional mutation manifests the mutant phenotype at high temperatures and is thus called a temperature-sensitive mutation. Temperature-sensitive dnaA mutants grow and replicate their DNA at the permissive temperature of 25°C, but they do not grow or replicate their DNA at the restrictive (non-permissive) temperature of 37°C. Two observations helped to determine the function of the dnaA gene product: • First, in vitro studies using DNA templates that have been unwound do not require the DnaA protein for DNA synthesis. Second, if intact cells are grown at 25°C and then shifted to 37°C, DNA synthesis continues at this temperature until one round of replication is completed, and then DNA synthesis stops. a. What two conclusions can you draw from these observations about the role of the dnaA gene product? b. Explain your answers.

Mutations in the dnaA gene of E. coli are lethal. Therefore, we can only study such mutations if we are able to generate conditional mutations (mutations whose effect takes place only in certain conditions). One type of conditional mutation manifests the mutant phenotype at high temperatures and is thus called a temperature-sensitive mutation. Temperature-sensitive dnaA mutants grow and replicate their DNA at the permissive temperature of 25°C, but they do not grow or replicate their DNA at the restrictive (non-permissive) temperature of 37°C. Two observations helped to determine the function of the dnaA gene product: • First, in vitro studies using DNA templates that have been unwound do not require the DnaA protein for DNA synthesis. Second, if intact cells are grown at 25°C and then shifted to 37°C, DNA synthesis continues at this temperature until one round of replication is completed, and then DNA synthesis stops. a. What two conclusions can you draw from these observations about the role of the dnaA gene product? b. Explain your answers.

Human Anatomy & Physiology (11th Edition)
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
Section: Chapter Questions
Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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Mutations in the dnaA gene of E. coli are lethal. Therefore, we can only study such mutations if we are able to generate conditional mutations (mutations whose effect takes place only in certain conditions). One type of conditional mutation manifests the mutant phenotype at high temperatures and is thus called a temperature-sensitive mutation. Temperature-sensitive dnaA mutants grow and replicate their DNA at the permissive temperature of 25°C, but they do not grow or replicate their DNA at the restrictive (non-permissive) temperature of 37°C. Two observations helped to determine the function of the dnaA gene product: • First, in vitro studies using DNA templates that have been unwound do not require the DnaA protein for DNA synthesis. Second, if intact cells are grown at 25°C and then shifted to 37°C, DNA synthesis continues at this temperature until one round of replication is completed, and then DNA synthesis stops. a. What two conclusions can you draw from these observations about the role of the dnaA gene product? b. Explain your answers.
Transcribed Image Text:Mutations in the dnaA gene of E. coli are lethal. Therefore, we can only study such mutations if we are able to generate conditional mutations (mutations whose effect takes place only in certain conditions). One type of conditional mutation manifests the mutant phenotype at high temperatures and is thus called a temperature-sensitive mutation. Temperature-sensitive dnaA mutants grow and replicate their DNA at the permissive temperature of 25°C, but they do not grow or replicate their DNA at the restrictive (non-permissive) temperature of 37°C. Two observations helped to determine the function of the dnaA gene product: • First, in vitro studies using DNA templates that have been unwound do not require the DnaA protein for DNA synthesis. Second, if intact cells are grown at 25°C and then shifted to 37°C, DNA synthesis continues at this temperature until one round of replication is completed, and then DNA synthesis stops. a. What two conclusions can you draw from these observations about the role of the dnaA gene product? b. Explain your answers.
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