[citation needed] Replication involves an RNA intermediate, as in viruses belonging to group VII of Baltimore classification.

[citation needed] Members of the family Hepadnaviridae encode their own polymerase, rather than co-opting host machinery as some other viruses do.

This enzyme is unique among viral polymerases in that it has reverse transcriptase activity to convert RNA into DNA to replicate the genome (the only other human-pathogenic virus family encoding a polymerase with this capability is Retroviridae), RNAse activity (used when the DNA genome is synthesized from pgRNA that was packaged in virions for replication to destroy the RNA template and produce the pdsDNA genome), and DNA-dependent-DNA-polymerase activity (used to create cccDNA from pdsDNA in the first step of the replication cycle).

[citation needed] The hepatitis envelope proteins are composed of subunits made from the viral preS1, preS2, and S genes.

The smallest envelope protein containing just the S subunit is made most because it is encoded closest to the 3' end and comes from the shortest transcript.

These envelope proteins can assemble independently of the viral capsid and genome into non-infectious virus-like particles that give the virus a pleomorphic appearance and promote a strong immune response in hosts.

[citation needed] Hepadnaviruses replicate through an RNA intermediate (which they transcribe back into cDNA using reverse transcriptase).

[6] Most hepadnaviruses will only replicate in specific hosts, and this makes experiments using in vitro methods very difficult.

The genome then undergoes transcription by the host cell RNA polymerase and the pregenomicRNA (pgRNA) is sent out of the nucleus.

Inside this capsid the genome is converted from RNA to pdsDNA through activity of the polymerase as an RNA-dependent-DNA-polymerase and subsequently as an RNAse to eliminate the pgRNA transcript.

[3][4] Based on the presence of viral genomes in bird DNA it appears that the hepadnaviruses evolved >82 million years ago.

[citation needed] Phylogenetic trees suggest that the bird viruses originated from those infecting reptiles.