Virology basics — In virus architecture, what exactly constitutes the nucleocapsid (state the two parts clearly)?

Introduction / Context:
The term nucleocapsid is foundational in virology and appears in diagnostic reports, vaccine papers, and antiviral targets. It precisely refers to the viral nucleic acid packaged together with its protective protein coat, the capsid. Understanding this term avoids confusion with other layers such as envelopes and spike glycoproteins.

Given Data / Assumptions:

• Nucleocapsid = nucleic acid + capsid (protein shell).
• Some but not all viruses also possess a lipid envelope with spikes.
• Capsomeres are the repeating protein subunits that assemble to form a capsid; they are not an alternative to the whole capsid.

Concept / Approach:
Disentangle the hierarchical structure: capsomeres assemble into a capsid; the capsid encloses the genome; genome + capsid = nucleocapsid. If present, an envelope (with spikes) surrounds the nucleocapsid but is not part of it by definition.

Step-by-Step Solution:

Verification / Alternative check:
Electron microscopy and structural biology textbooks consistently define nucleocapsid as genome + capsid. Enveloped viruses have an added lipid bilayer, but the core concept remains the same across families.

Why Other Options Are Wrong:

• Capsid and spikes: spikes are envelope proteins, not part of the nucleocapsid.
• Envelope and capsid: the envelope is optional and external.
• Capsomere and genome: capsomere is a subunit, not the assembled capsid.

Common Pitfalls:
Equating the presence of spikes with the definition of the core particle; assuming envelopes are universal. Many clinically significant viruses are nonenveloped and still have a nucleocapsid.

Final Answer:
Genome and capsid