Sample questions for MT-2, Fall/2012
1. Describe the role of the following components in ColE1 biology.
2. You have been given a strain of E. coli carrying a mutation in the lexA gene. What will
the relative mutation rate of this strain be compared to a wild type E. coli strain? How
will this strain survive UV irradiation compared to the wild type strain?
3. A lacZ- mutant was recovered at a frequency of approximately 10 . The mutant also
acquired resistance to ampicillin simultaneously. You suspected that it might have been
caused by the integration of a Tn3 into the lacZ gene. You have obtained the nucleotide
sequence of the mutated lacZ gene for comparison with the wild-type lacZ sequence.
Describe three characteristics of the sequences that support the hypothesis of Tn3
insertion into the lacZ gene.
4. A Tet plasmid carries a temperature sensitive mutation in its origin of replication and
cannot replicate at 42 C. This plasmid was introduced into Tet E. coli cells to produce