The nucleic acid found in virus can be either DNA or RNA. On the basis of number of strands present in nucleic acid they are further cate gorised as:
(i) Single stranded DNA virus: Bacteriophage ϕ×174, coliphage S13, Bacteriophage M13.
(ii) Double stranded DNA virus: Adenovirus, Chickenpox, small pox, coliphage T2,T4,T6,T3,T7, Lambda coliphage.
(iii) Single stranded RNA virus: TMV, Influenza, Rhinovirus, AIDS, polio, rabies, coliphage R17.
(iv) Double stranded RNA virus: Wound tumour virus, rice dwarf virus, reovirus.