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A mutant strain of T4 bacteriophage, r-II, fails to lyse E. coli but when two strains r-IIx and r-IIy are mixed then they lyse E. coli. What may be the possible reason : -
A
Bacteriophage transforms in wild
B
It is not mutated
C
Both strains have similar cistrons
D
Both strains have different cistrons
Detailed Solution
Seymour Benzer studied rII mutants of T4 phage, which cannot grow on E. coli strain K.
When two different rII mutants infect the same cell together, they can complement each other only if the mutations are in different functional units (cistrons A and B). Each phage supplies the product that the other lacks, so the bacterium is lysed.
If both mutations were in the same cistron, neither could supply that function and there would be no lysis.
So the two strains lyse E. coli together because they have mutations in different cistrons.
When two different rII mutants infect the same cell together, they can complement each other only if the mutations are in different functional units (cistrons A and B). Each phage supplies the product that the other lacks, so the bacterium is lysed.
If both mutations were in the same cistron, neither could supply that function and there would be no lysis.
So the two strains lyse E. coli together because they have mutations in different cistrons.