Notes on Family: Birnaviridae
This family consists of viruses that infect animals (vertebrates, insects, molluscs and crustaceans) and which have double stranded RNA genomes in two components (bi-RNA-vir
uses). The isometric virions (60 nm) are much larger than those in the family Partitiviridae
, whose members infect plants or fungi.
Virions isometric (icosahedral), not enveloped, 60 nm in diameter, made of 260 units trimeric subunits.
Bipartite double-stranded RNA totalling 5.8-6.5 kb with a genome-linked protein (VPg) at the 5'-termini. There is no 3'-polyA tail. Each segment encodes a large polyprotein that it is subsequently processed into the functional products and there is an additional, smaller ORF on the larger (A) segment. The capsid proteins are encoded on segment A and an RNA-dependent RNA polymerase on segment B.
Genera in the Family