What is the structural form of RNA?

its a evolutionary structure before DNA .here too nucleotides are present except thymine. Uracil is present in place of thymine with three hydrogen bonds with guanine.Its codon decided by complementary sequence of template strand of DNA.More over there is many types of RNA like SnRNA,tRNA(clover leaf modal in 3-D or L- shaped model in 2-D) etc.u should get information with diagrams from RNA related website.