Here's a breakdown:

* DNA in the nucleus: Contains the genetic code for making proteins.

* Transcription: DNA is transcribed into mRNA, which is a copy of the genetic code for a specific protein.

* mRNA leaves the nucleus: Travels to the ribosome in the cytoplasm.

* Translation: Ribosomes use the information in the mRNA to assemble amino acids into a protein.

So, mRNA acts as the messenger, carrying the instructions from the DNA in the nucleus to the ribosomes, where the protein is actually built.