Final answer:
RNA transcription occurs as RNA polymerase synthesizes mRNA in the 5' to 3' direction while reading the DNA template from the 3' to 5' direction. Once initiated at the promoter site, transcription stops upon reaching a termination sequence.
Step-by-step explanation:
During the process of RNA transcription, the enzyme called RNA polymerase synthesizes a strand of messenger RNA (mRNA) in the 5' to 3' direction. This happens as the RNA polymerase reads the DNA template strand from its 3' to 5' direction. Essentially, RNA nucleotides are added to the growing mRNA molecule in a manner that is complementary to the DNA template. The binding at the promoter site ensures that RNA polymerase is appropriately positioned to begin transcription. Within the transcription bubble, as the enzyme progresses, it unwinds the double-stranded DNA in front of it and rewinds it afterward, making sure the mRNA is an accurate copy of the gene's coding sequence, with uracil (U) replacing thymine (T) where adenine (A) appears on the DNA strand.
After this initial synthesis, in eukaryotes, the mRNA may undergo additional processing in the nucleus before it is transported to the cytoplasm for translation, where ribosomes read the mRNA sequence to synthesize the corresponding protein. Transcription ceases when RNA polymerase reaches a termination site, releasing the newly formed mRNA from the DNA template.