How does transcription work?

Transcription is the first step of protein synthesis and occurs within the nucleus of the cell. Within the cell's nucleus is the DNA. Firstly an enzyme called DNA Helicase 'unzips' the two DNA strands separating them. It does this by breaking the hydrogen bonds between the complementary base pairs of the DNA (A /T and C/G). There are also free RNA nucleotides within the nucleus which will be used to make an RNA copy of the template DNA strand (the strand you want to copy). These are the same as the nucleotides making up DNA (C,G,U,T) apart from there is U instead of T. These free nucleotides pair with their complementary base on the template DNA strand by complementary base pairing forming hydrogen bonds. The enzyme RNA polymerase joins the nucleotides together. This forms the premRNA copy. This is converted to mRNA through splicing where the non coding introns are removed.