There are 6 ways in which viroids are different to viruses:(i) Contain single circular RNA of low molecular weight (300 to 400 nucleotides).(ii) RNA is often internally paired (3D) and is therefore protected against cellular Enzymes.(ii) Viroids contain no capsids or envelopes.(iii) There is no requirement for helper viruses.(iv) Viroids do not produce proteins.(v) In viroids RNA is always copied in the host cell nucleus.(vi) Viroids can only be identified by nucleotide sequencing techniques.