Answer
The mRNA molecule would have first been created within the nucleus where it read the DNA code for this particular protein. This is called transcription. After transcription the mRNA molecule would leave through the nuclear pore and go to a ribosome at the rough ER for the next phase of protein synthesis called translation. During translation the mRNA sequence is read and amino acids are brought by tRNA to build a polypeptide chain. After a stop codon is reached the polypeptide would get folded into a 3D shape in the transitional ER. After folding the polypeptide can now be referred to as a protein. A transport vesicle would form around this protein and deliver it to the Golgi. At the Golgi it would mature through the use of various enzymes and at full maturation the vesicle would then fuse away from the Golgi and go back to the ER where it would fuse within the ER and the protein will now be functional with the ER.
Work Step by Step
Proteins are created based on a DNA code. The DNA is within the nucleus so we start here. Protein synthesis follows a progression from nucleus to the ribosome. At a ribosome the polypeptide is build but it is not yet functional. It becomes functional once it is folded. This can only be done by the ER. Even after folding some proteins are not mature until they travel to the Golgi for further "tweaking." After this is complete the protein is fully functional and it may follow various routes to get to where it needs to go. In general the locations within the cell in order would be: nucleus, ribosome, ER, Golgi
