According to Chargaff’s rule the composition of all the four purines (adenine, thymine) and pyrimidines (guanine, cytosine) would be equal. The ration of A = T and G = C are equal to one. The composition, for coli phage is different from that of Chargaff’s rule.
A difference in the composition of the nucleotides as opposed to the Chargaff’s rule denotes that the DNA could be a single stranded.
The DNA of a phage after entering the host bacterial cell would first synthesize its complementary strand. Only after the synthesis of the complementary strand, the phage DNA initiates its multiplication of genome copies.