Genetic analyses have contributed significantly to our understanding o
f the biology of the rotaviruses. The distinguishing feature of the vi
rus is a genome consisting of 11 segments of double-stranded RNA. The
segmented nature of the genome allows reassortment of genome segments
during mixed infections, which is the major distinguishing feature of
rotavirus genetics. Reassortment has been a powerful tool for mapping
viral mutations and other determinants of biological phenotypes to spe
cific genome segments. However, more detailed genetic analysis of rota
viruses is currently limited by the inability to perform reverse genet
ics. Development of a reverse genetic system will facilitate analysis
of the molecular mechanisms involved in various genetic, biochemical,
and biological phenomena of the virus.