The DNA strand being read by the RNA polymerase is called the DNA template. RNA polymerases always produce mRNA strands that are complementary and antiparallel. Complementary means the bases of DNA and RNA will align in this particular manner (A-U and G-C). Antiparallel means that the DNA and RNA strand will have opposite direction. Therefore, RNA polymerase will read the DNA template in 3’ – 5’ direction and synthesize mRNA strand in the 5’ - 3’ direction.