Gene Cloning and Recombination. Not only are the plasmid vectors used in molecular biology engineered, but the strains of $E .$ coli used in cloning are as well. (a) Nearly all strains of $E .$ coli used in DNA cloning carry mutations in the recA gene that result in loss of RecA activity. Why would a recA mutation make an $E .$ coli cell a better host for propagating recombinant plasmid DNA? (b) Recall that restriction endonucleases are normally made by bacteria such as $E .$ coli (Box 18B, page 520). $E$ coli used in molecular biology also carry mutations in restriction endonucleases. Why do you think these mutations would be useful?
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coli. A mutation in the recA gene that results in loss of RecA activity would make an E. coli cell a better host for propagating recombinant plasmid DNA because it would reduce the chances of unwanted recombination events between the plasmid DNA and the host's Show more…
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Before a desired gene can be spliced into a bacterial plasmid cloning vector, the gene must first be isolated from the original DNA. a. cloned from the mix of recipient DNA b. injected into a stem cell to determine any unwanted traits c. injected into a bacterial cell or a virus having different sequences d. precisely cut with a restriction enzyme 6. Arrange the following events in the proper sequence for gene cloning. 1 = Fragment DNA with a restriction enzyme 2 = Isolate DNA from the organism containing the desired gene 3 = Incorporate the cloned gene into bacterial cells 4 = Incorporate the gene into a bacterial plasmid a. 1, 2, 3, 4 b. 2, 1, 4, 3 c. 4, 1, 2, 3 d. 3, 2, 1, 4 7. Plasmids are __ a. Circular pieces of DNA that are part of a bacterial chromosome. b. Separate pieces of DNA, which are not part of a bacterial chromosome. c. Contain genes for specialized functions. d. A & B e. B & C 8. Competent cells more readily take up DNA because their cell walls have been altered. a. take up DNA; cell walls b. release DNA; cell membrane c. replicate plasmids; cytoplasm d. grow and divide in log phase; cell walls
a) Explain what would happen to DNA replication in a strain of E. coli that had a mutation in the gene for DNA ligase? b) Explain what would happen to DNA replication in a strain of E. coli that had a mutation in the gene for DNA polymerase I? c) Explain what would happen to DNA replication in a mutant strain of E. coli that had a mutation in the gene for primase?
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