In viruses, which of the following describes a possible structure of the viral genome?

• A. Single-stranded or double-stranded nucleic acid that may be linear, circular, or segmented
• B. Protein-only genetic material lacking any nucleic acid
• C. Only single-stranded RNA that is always linear and unsegmented
• D. Only double-stranded DNA that is always circular and unsegmented

Answer: (A)

Verified step by step guidance

1. Understand that viral genomes can be composed of nucleic acids, which are either RNA or DNA, but never protein alone. This rules out the option stating 'Protein-only genetic material lacking any nucleic acid.'
2. Recognize that viral genomes can be single-stranded or double-stranded, depending on the virus type. This means the genome is not restricted to only single-stranded RNA or only double-stranded DNA.
3. Know that the shape of viral genomes can vary: they may be linear, circular, or segmented. Segmented genomes mean the genetic material is divided into separate pieces rather than one continuous strand.
4. Eliminate options that restrict the genome to only one type of nucleic acid structure (e.g., only single-stranded RNA or only double-stranded DNA) or only one shape (e.g., always linear or always circular).
5. Conclude that the correct description of viral genomes is that they can be single-stranded or double-stranded nucleic acid, which may be linear, circular, or segmented.