Researchers Have Isolated a Mutant Strain of E

Essay

Researchers have isolated a mutant strain of E.coli that carries a temperature-sensitive variant of the enzyme DNA ligase.At the permissive temperature, the mutant cells grow just as well as the wild-type cells.At the nonpermissive temperature, all of the cells in the culture tube die within 2 hours.DNA from mutant cells grown at the nonpermissive temperature for 30 minutes is compared with the DNA isolated from cells grown at the permissive temperature.The results are shown in Figure 6-59, where DNA molecules have been separated by size by means of electrophoresis (P, permissive; NP, nonpermissive).Explain the appearance of a distinct band with a size of 200 base pairs (bp) in the sample collected at the nonpermissive temperature.
Figure 6-59