 The smallest double-stranded DNA viruses are the hepadnaviruses such as Hepatitis B, at 3.2 kb and 42 nm; parvoviruses have smaller capsids, at 18-26 nm, but larger genomes, at 5 kb.It is important to consider other self-replicating genetic elements, such as satelliviruses, viroids and ribozymes.The genome of "Nasuia deltocephalinicola", a symbiont of the European pest leafhopper, "Macrosteles quadripunctulatus", consists of a circular chromosome of 112,031 base pairs.