DNA helicase acts on the part of the DNA strand that is to be transcribed, usually a specific gene. It unwinds the strand and breaks the hydrogen bonds.
RNA polymerase then links to the DNA at the start of the sequence that is to be copied.
Only the template strand is used for transcription. This is the part that has complimentary bases to those required for the correct amino acid sequence.
Free activated RNA nucleotides align with the complimentary bases and bond using hydrogen bonds, A to U and G to C.
RNA polymerase then moves along this strand, forming the sugar-phosphate backbone of the mRNA molecule. The energy from this comes from removing the extra phosphate…