Baltimore/Bradley perspective: Group E bacteriophages are characterized by which type of nucleic acid?

Introduction:
Historic bacteriophage classifications (e.g., Bradley groups) and broader genome-type schemes highlight that some coliphages, such as MS2 and related male-specific phages, possess RNA genomes. Recognizing which group corresponds to RNA phages is a common exam objective.

Given Data / Assumptions:

• The question refers to “Group E phages,” a classic morphology/genome grouping.
• Representative members include small icosahedral phages like MS2.
• We must select the correct nucleic acid type.

Concept / Approach:
Group E phages (male-specific, leviviruses) have positive-sense single-stranded RNA genomes. They infect bacteria via F pili and are distinct from the large dsDNA tailed phages. Their compact genomes encode maturation, coat, lysis, and replicase proteins.

Step-by-Step Solution:
Recall examples: MS2, f2, Qβ-like phages. Associate these with +ssRNA genomes and small icosahedral capsids. Select “single-stranded RNA.”

Verification / Alternative check:
Classic literature and modern databases list MS2 as a positive-sense ssRNA phage, aligning with Group E designation in older schemes.

Why Other Options Are Wrong:

• Single-/Double-stranded DNA: Describe many tailed phages, not Group E RNA phages.
• Double-stranded RNA / Segmented dsDNA: Not characteristic of MS2-like coliphages.

Common Pitfalls:
Confusing Baltimore numbering (I–VII) with older lettered phage groups; cross-checking exemplars like MS2 prevents errors.

Final Answer:
Group E phages possess single-stranded RNA genomes.