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RNA Polymerase
The enzyme that polymerizes RNA using DNA sequence as a template to make an mRNA molecule
Promoter
The sequence of DNA found just before (upstream of) the start of the coding part of a gene that tags the "starting point" of the gene; the sequence where RNA polymerase will initially bind to transcribe a gene
mRNA
"messenger" RNA, the copy of a gene in RNA that will be used by the ribosome for translation