Final answer:
Nanos is localized to the posterior end of the cell through a process called receptor-mediated endocytosis.
Step-by-step explanation:
Nanos is localized to the posterior end of the cell through a process called receptor-mediated endocytosis. During this process, the substance to be internalized binds to cell membrane receptors, causing the receptors to cluster and form coated pits. The coated pits then invaginate and pinch off to form coated vesicles, which bring the extracellular contents into the cell. This mechanism is driven by the affinity of the receptors for specific substances and is well understood in bringing larger substances into cells.