Comparative genomics — Across sequence comparisons, where would you expect greater similarity: among viruses themselves or between viruses and their specific hosts?

Introduction / Context:
This question probes evolutionary relationships and sequence homology expectations in host–virus systems. Despite viral diversity, many viruses evolve from and adapt to specific host cellular environments, often sharing motifs with host factors they hijack.

Given Data / Assumptions:

• Viruses are highly diverse across families and genome types (DNA/RNA, ss/ds, segmented/nonsegmented).
• Host genomes are far larger but contain proteins and motifs that viruses target or mimic.
• We are comparing overall similarity trends, not cherry-picked genes.

Concept / Approach:
Because of extreme viral diversity, inter-virus similarity across unrelated families is typically low. Conversely, specific viral proteins (or sequence motifs) may resemble host proteins, interaction domains, or regulatory sequences due to convergent evolution, mimicry, or gene capture. Hence, measured similarity can be higher between a virus and its host than between two unrelated viruses.

Step-by-Step Solution:

Verification / Alternative check:
Comparative analyses often reveal host-derived sequences in large DNA viruses and host-like interaction motifs in many RNA viruses, elevating virus–host similarity relative to cross-family virus–virus comparisons.

Why Other Options Are Wrong:

• Among different viruses: too diverse to be generally more similar.
• Among different hosts: question focuses on virus–host versus inter-virus similarity.
• Among hosts vs viruses: misframes the comparison.

Common Pitfalls:
Assuming “all viruses are similar” because of shared small size; in reality, genome strategies differ profoundly across lineages.

Final Answer:
Between viruses and their hosts than among different viruses