AP BIOLOGY

Detailed explanation-1: -Viroids are infectious agents that consist only of naked RNA without any protective layer such as a protein coat. Viroids infect plants (but no other forms of life) and are replicated at the expense of the host cell. Viroid genomes are small single-stranded circles of RNA that are only 250–400 bases long.

Detailed explanation-2: -Viroids are single-stranded, covalently closed, circular, highly structured noncoding RNAs that cause disease in several economically important crop plants. They replicate autonomously and move systemically in host plants with the aid of the host machinery.

Detailed explanation-3: -Viroids are the only known autonomously replicating pathogenic agents that do not encode proteins. As viroids are known only to naturally infect plants, their infectivity and pathogenicity in other eukaryotes are largely unexplored.

Detailed explanation-4: -Viroids are infectious pathogens that affect only plants, therefore are also called plant pathogens.

Detailed explanation-5: -Viroids are single-stranded, covalently closed circular RNA molecules. As a distinct class of pathogens, they are clearly distinguished from viruses by their small size (∼250–400 nt), do not encode any protein and lack a capsid.