this is bit complicated but once u get it it's very useful....
PCR causes amplification so will fill FAT BORA SO
to remember there symmetry use a bit of immagination...
first letter of all 3 is HELICAL i.e paramyxo,flavi,bunya
picorna has i so ICOSAHEDRAL
calcivi and corona both starts with c but
calicivi has i so ICOSAHEDRAL
corona is COMPLEX
retrovirus we know r diff from others so COMPLEX
rhabdo has h so HELICAL
filo been d first in fat is HELICAL
flavi is compared to flavour which is a complex sensation so COMLPEX
astro & toga both r ICOSAHEDRAL
bunya is HELICAL
orthomyxo same as paramyxo so HELICAL
reo is ICOSAHEDRAL
arena..thinking of arena as karena kapoor is a complex thought so COMPLEX
ALL HELICAL AND COMPLEX R ENVELOPED
ONLY ICOSAHEDRAL WHICH IS ENVELOPED IS togaviridae..