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.

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Description: Mutations in the dnaA gene of E. coli are lethal. Therefore, we can only study such mutations ifwe are able to generate conditional mutations (mutations whose effect takes place only in certainconditions). One type of conditional mutation manifests

Biology Today and Tomorrow without Physiology (MindTap Course List)

5th Edition

ISBN:9781305117396

Author:Cecie Starr, Christine Evers, Lisa Starr

Publisher:Cecie Starr, Christine Evers, Lisa Starr

Chapter10: Biotechnology

Section: Chapter Questions

Problem 1CT

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