Final answer:
Most single-stranded DNA phages, such as bacteriophage M13, must synthesize a complementary strand to form double-stranded DNA before replication and transcription, known as the 'replicative form' which acts similarly to a plasmid within the host.
Step-by-step explanation:
The answer is c. Have their DNA transformed to double-stranded DNA before replication and transcription occur. Most phages, including the well-studied bacteriophage M13, which contains single-stranded DNA, must synthesize a complementary strand to become double-stranded (forming what is called the replicative form) before replication and transcription can take place. This replicative form behaves much like a plasmid within E. coli, which can then use it for rDNA technology.
The lytic and lysogenic cycles are relevant to this question because they represent two different pathways that phages can undergo after infecting a host cell. In the lytic cycle, phages replicate inside the host cell and eventually cause the host cell to lyse and release new virions. In contrast, during the lysogenic cycle, phage DNA is incorporated into the host genome, allowing it to be replicated along with the host's DNA and passed on to subsequent generations. Environmental stress can trigger the switch from lysogenic to lytic cycle, leading to phage replication and cell lysis.