Final answer:
Step 3 in the lytic cycle refers to the biosynthesis of new viral components, while in the lysogenic cycle it involves the integration of phage DNA into the host genome, forming a prophage.
Step-by-step explanation:
Step 3 of both the lytic and lysogenic cycles of a bacteriophage involves complex interactions between the phage DNA and the host bacterium. In the lytic cycle, step 3 is the biosynthesis of viral components. The phage DNA directs the synthesis of virus-encoded enzymes that degrade the bacterial chromosome and hijacks the cell's machinery to replicate viral components necessary for assembling new viruses. In contrast, during the lysogenic cycle, phage DNA integrates into the host genome at step 3, forming a prophage that can be replicated and passed to subsequent generations of the bacterium. The prophage can remain dormant for many cell cycles, but environmental stressors can trigger it to re-enter the lytic cycle.