Most genetic material, both DNA and RNA, appears as two chains or strands of nucleotides wound together into a double helix. The common picture of DNA. Each nucleotide - A, T, C and G - has an attractive opposite (C attracts G, A attracts T). As a result, one strand, the “sense” strand, contains the information (for example, ATG-AAA) and the other strand, the “antisense” strand contains the opposite of this information (TAC-TTT according to the pairing rules). Antisense RNA is the “antisense” half of a complete double RNA strand. RNA viruses consist of two types, “sense” RNA viruses, whose genetic material consists of the “sense” half of a complete strand, and “antisense” RNA viruses, which have the “antisense” half. Sense RNA viruses can have their genetic material read out directly by the ribosomes of their host cells - antisense RNA viruses must first copy themselves into a “sense” strand of RNA