Now that RNA polymerase has bound the gene, it begins reading the DNA in the 3’ to 5’ direction (just like DNA polymerase), forming a complementary strand of RNA. This means that the mRNA strand forms in the 5’ to 3’ direction. When the polymerase has completed its task, it falls away and goes off to read another gene. We’re left with a transcript, a molecule of messenger RNA that contains instructions for making a particular protein. But the mRNA must first undergo three important modifications: it has to grow a tail, it has to put on a hat, and it has to get spliced.