Final answer:
Platelets do not have a nucleus at any stage of their life cycle. They are fragments derived from megakaryocytes in the bone marrow, which have a nucleus that is consumed by macrophages after platelet release.
Step-by-step explanation:
Do platelets have a nucleus throughout any part of their life cycle? No, platelets do not have a nucleus at any point in their life cycle. Platelets are small, typically 2-4 µm in diameter, fragments of cytoplasm that are derived from the cells called megakaryocytes within the bone marrow. Megakaryocytes do have a large, lobed nucleus, but as they mature, they extend cytoplasmic processes through the bone marrow vessel walls and shed off thousands of cytoplasmic bits enclosed in a plasma membrane, which become platelets. Following the release of platelets, the remnant of the megakaryocyte, mostly the nucleus, is consumed by macrophages, meaning that platelets themselves never contain a nucleus.