What fluid is found within the nucleus and contains proteins and DNA?

The fluid found within the nucleus that contains proteins and DNA is known as nucleoplasm. This semi-fluid environment plays a crucial role in maintaining the shape of the nucleus and providing a medium for the biochemical processes occurring within it. The nucleoplasm is similar to cytoplasm but is specifically tailored for the activities of the nucleus, including the replication of DNA and the synthesis of RNA.

Unlike cytoplasm, which is the gel-like substance within the entire cell surrounding the nucleus, nucleoplasm only refers to the substance found within the nuclear envelope. Protoplasm is a broader term that includes the cytoplasm and nucleoplasm combined but does not refer specifically to the fluid in the nucleus itself. The cell membrane is a barrier that encloses the entire cell and does not pertain to any fluid within the nucleus. Thus, nucleoplasm fits the description best as it is distinctively where the genetic material exists and where many essential nuclear functions take place.