A Gene is a length of DNA that codes for a protein
Step 1 : Example Insulin
mRNA copy the instructions (gene) for insulin is made in the nucleus.
mRNA leaves the nucleus through the nuclear pore.
mRNA attaches itself to a ribosome in this case attached to the endoplasmic reticulum. The ribosome reads the instructions to assemble the protein.
Insulin molecules are 'pinched off' in a vesicle and travels towards the golgi apparatus.
vesicles fuse with the golgi apparatus
The Golgi apparatus processes and re-packages the insulin molecules ready for release.
The packaged insulin molecules are pinched off in vesicles from the golgi apparatus and move towards the cell surface membrane.
The vesicles fuse with the cell surface membrane .
Cell surfrace membrane opens to release the insulin molecules outside. ready for use.