Under the effect mainly of an enzyme, RNApolymerase (2), DNA (1) is split into two strands: On the non-transcribed strand (template strand) (3), nucleosidetriphosphates (5) form portions of mRNA chains (6) whose base sequence is identical to that of the transcribed strand (nontemplate strand) (4):
Image from → Wikipedia
This process is analogous to the duplication of the DNA seen → here except that the nucleosidetriphosphates do not derive from deoxyribose but from ribose:
and thymine is replaced by uracil:
Very special base sequences on the non-transcribed strand (3) inform the polymerase (2) where to start and end the transcription. The transcribed portions of DNA are called "genes". See about this subject the excellent article details → here The different mRNAs will then leave the nucleus carrying the codes of the genes to the ribosomes where protein synthesis takes place.
