A genetic mutation prevents the proper glycosylation and folding of proteins destined for secretion or insertion into the plasma membrane. Which cellular organelle is most likely directly affected by this mutation?

✓ Correct Answer: Option C

The rough endoplasmic reticulum (RER) is the site where proteins destined for secretion, membrane insertion, or delivery to lysosomes are synthesized, folded, and undergo initial glycosylation. Impairment here would disrupt these processes.