Final answer:
Prokaryotes lack a true nucleus, unlike eukaryotes which have a nucleus that contains the genetic material controlling cellular function.
Step-by-step explanation:
Eukaryotes such as animal and plant cells differ from prokaryotes in that prokaryotes lack a true nucleus. Eukaryotic cells have a nucleus that houses the genetic material, or DNA, that controls cellular function. Prokaryotes have their genetic material contained in a nucleoid, which is not surrounded by a membrane.