Final answer:
The incorrect statement about bacteriophages is (D), which suggests that they can pack the main chromosome from one bacterial cell and transfer it to another. Bacteriophages may transfer DNA fragments but not the complete bacterial chromosome.
Step-by-step explanation:
To address the question regarding which statement about bacteriophages is not true, we need to look closely at the characteristics of these viruses. Bacteriophages are indeed viruses that infect bacteria (bacterial cell). They use the host's metabolic machinery to produce more copies of themselves (A is true). Furthermore, they can pick up bacterial genes during infection, a process known as transduction (B is true). In the lysogenic cycle, phage DNA can integrate into the host genome, which explains how they can transfer genetic material between cells (C is true).
The incorrect statement is (D), 'Within their heads, they can pack the main chromosome from one cell and transfer it to another.' While bacteriophages can accidentally package host DNA during the formation of new virions, they do not intentionally pack and transfer the host's main chromosome as described. Instead, fragments of DNA may be transferred during specialized or generalized transduction, but not the entire chromosome.