Why bacteriophages are model systems: Bacteriophages are widely used in genetic research because they are the smallest and simplest biological entities capable of what property?

Introduction / Context:
Bacteriophages (viruses that infect bacteria) have powered milestones in molecular biology—from the genetic code to DNA replication mechanisms. Their utility comes from genetic simplicity paired with the ability to replicate using host machinery.

Given Data / Assumptions:

• Phages carry nucleic acid genomes encased in protein coats.
• They cannot metabolize independently but direct host systems to produce progeny virions.
• The question asks for the key capability that makes them powerful genetic tools.

Concept / Approach:
Despite metabolic dependence on hosts, phages are capable of self-replication in the biological sense: their genomes encode the information required to direct the production of more of themselves within suitable hosts. Terms like “duplication” or “multiplication” are colloquial and imprecise; “self-replication” is the standard biological term emphasizing template-directed propagation.

Step-by-Step Solution:
Focus on biological property: information-directed replication of the entity.Select the precise term “self-replication.”Reject synonyms that lack precise biological usage in this context.

Verification / Alternative check:
T-even phages (e.g., T4) demonstrate orderly replication cycles with assembly of progeny phage—an archetype of self-replication guided by genetic information.

Why Other Options Are Wrong:
“Duplication,” “self-duplication,” and “multiplication” are vague and nonstandard relative to “self-replication,” the accepted term in genetics and molecular biology.

Common Pitfalls:
Assuming “self-replication” requires metabolic autonomy; in virology, replication refers to information-driven reproduction within a host system.

Final Answer:
self-replication