Question

A mutant strain of T4 – Bacteriophage, R-II, fails to lyse the E-Coli but when two strains RIIX and R-IIY are mixed then they lyse th E.Coli. What may be the possible reason

• A. Bacteriophage transforms in wild
• B. It is not mutated
• C. Both strains have simillar cistrons
• D. Both strains have different cistrons

Answer 1

Answer: (D)

Both strains have different cistrons

Answer 2

In this case, the mutant strain R-II has a mutation that prevents it from effectively lysing E. coli. However, when strains R-II-X and R-II-Y are mixed, they complement each other because they carry different mutations (different cistrons) that, when combined, restore the phage's ability to lyse E. coli. This phenomenon is known as complementation, where two strains with different mutations can restore a wild-type (functional) phenotype when combined. So, the correct option is (D): Both strains have different cistrons