Date of Award


Degree Type


Degree Name

Master of Science (MS)


Biological Sciences

First Advisor

Dr. Robert H. Rothman


The recA mutant has been shown to be completely recombination deficient and highly UV-sensitive. Also, this mutant is remarkably deficient in inducible "SOS" DNA repair and, consequently it is not UV-mutable and it cannot perform W-reactivation, an inducible non-excision repair dependent enhancement of phage recovery. The recB-recF- double mutant like the recA mutant, is recombination deficient and UV-sensitive.

As observed, each of these mutations appear to block an independent pathway of genetic recombination.

We are interested in determining how closely the recB-recF- double mutant resembles the recA mutant. In this perspective we looked at the W-reactivation of double stranded bacteriophage λ and single stranded bacteriophage fd.

On examining the W-reactivation for phage λ, it is seen that the recB- and recF- mutants separately lead to a reduction of UV-reactivation efficiency but when spliced, the recB-recF- double mutant further leads to a reduction of W-reactivation even though this is still significant in magnitude when compared to the results obtained for the recA mutant. In the recA mutant W-reactivation capability is totally absent.

Contrary to our results with bacteriophage λ , the recB- and recF mutants individually show enhanced W-reactivation of fd phage. The double mutant recB-recF- however, shows virtually no UV-reactivation potential. This is the same case for recA- mutant. Host-cell reactivation - an excision repair dependent potential was examined in the fd phage, λ vir and Pl vira. Our results demonstrate that host-cell recovery is non-existent in fd phage. On the other hand, we noticed high levels of phage recovery in λ vir and Pl vira.

We have demonstrated that although recB-recF- double mutant closely resembles the recA single mutant in their UV-sensitivity and recombination profile, this resemblance is seen to be parallel when their UV-inducible capability is examined in double stranded bacteriophages.

We therefore conclude that there are significant levels of inducible "SOS" DNA repair occurring in the recB- and recF- mutants and not in the double mutant, recB-recF-. This is due to the fact that there are genetic differences in the inducible DNA repair capability of single stranded and double stranded bacteriophages.