Answer:
1. Nucleus
2. RNA polymerase
3. mRNA
Step-by-step explanation:
Transcription is the first process of gene expression in which a DNA strand is used to synthesize a mRNA molecule. In the process of transcription, which occurs in the NUCLEUS, an enzyme called RNA polymerase binds to the DNA molecule.
The enzyme separates the double stranded DNA and the uses the complementary base pairing rule i.e. A-U, G-C to synthesize a mRNA molecule that is complementary to the DNA template strand. This newly built mRNA molecule then leaves the nucleus and enters the cytoplasm of the cell for translation to occur.