Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 11

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. E. coli used in molecular biology also carry mutations in restriction endonucleases. Why do you think these mutations would be useful