There are some similarities between prokaryotic and eukaryotic cells. What structures is found in both prokaryotic and eukaryotic cells?

DNA, ribosomes, plasma membrane and cytoplasm are the structures that are found in both.

Explanation:

Prokaryotes are the organisms that do not have a nucleus and other membrane-bound organelles and eukaryotes have a membrane-bound nucleus and another membrane-bound organelle.  

Apart from this there are some similarities between prokaryotic and eukaryotic cell like both have a highly selective cell membrane, they both have cytoplasm, both have DNA and ribosomes which is responsible for the expression of genes. Therefore DNA, ribosomes, plasma membrane, and cytoplasm are the structures that are common in both prokaryotes and eukaryotes.