Practice question

Viroids represent subviral pathogens composed solely of small, non-coding, single-stranded circular RNA without encapsidation or protein synthesis capability. Ranging from 246 to 401 nucleotides, they form highly base-paired rod-like secondary structure conferring resistance to nucleases that hijack host RNA polymerase II for replication via rolling circle mechanism. Infecting higher plants causing diseases like potato spindle tuber, they replicate in nucleus or chloroplast. Absence of capsid distinguishes them from viruses. Small size, circularity and lack of protein coat are diagnostic features separating viroids from virusoids and satellites.