Question

Bacterial cells were coinfected with two types of bacteriophage lambda: One carried the c+ allele and the other the c allele. After the cells lysed, progeny bacteriophage were collected. When a single such progeny bacteriophage was used to infect a new bacterial cell, it was observed in rare cases that some of the resulting progeny were c+ and others were c. Explain this result.

Answer 1

Since the cells are being coinfected by 2 types of viruses, this can create heteroduplex areas. DNA repair systems normally correct the heteroduplex areas. In rare cases, the heteroduplex is not corrected and a chromosome containing the mismatch appears so a single bacteriophage particle can be generated. One DNA strand is c+, and the other strand is c. When such a bacteriophage infects a fresh bacterial host cell, some molecules are created by DNA replication.