DNA and RNA are both composed of linear polymers of nucleotides, but their bases and sugars differ. DNA contains deoxyribose and thymine, while RNA contains ribose and uracil. DNA is double- stranded while RNA is single-stranded. RNAs are capable of forming stable, functional and complex stem-loop structures. DNA is wound in a double helix and packaged by proteins into chromosomes. DNA functions as a storage molecule, while RNA functions variously as a messenger, in the process of translation, and in eukaryotic RNA processing. Both polymerases catalyze the synthesis of nucleic acids in the 5' to 3' direction. Both use a DNA template and synthesize a nucleic acid polynucleotide that is complementary to the template. DNA polymerases require a 3'-OH to add onto while RNA don't. RNA polymerases can initiate chains without primers, while DNA can't. RNA polymerases usually require specific base-pair sequences as signals to initiate transcription.
