Two different strains of a mutant phage infect a single bact

Two different strains of a mutant phage infect a single bacterium. One phage strain is d–e+ and the other is d+e–. The coinfected phages produce the wild-type phenotype in the bacterium: one phage supplies the wild-type gene product from a d+ allele, and the other supplies the wild-type gene product from the e+ allele. What genetic phenomenon does this demonstrate?

   a.  
complementation

   b.  
specialized transduction

   c.  
recombination

   d.  
generalized transduction

   e.  
both a and b are correct

   f.  
both a and c are correct

   g.  
both b and c are correct

   h.  
both a and d are correct

Solution

Answer: (a) Complementation.

The phenotype indicates that the two mutations complement each other, i.e, one phage supplies the d+ while the other supplies the e+ gene product.

Its not recombination (which includes transduction) because recombination would have produced the auxotrophs, i.e, d+e- and d-e+ as well along with the wild type (d+e+).