What is the spherical body found in the nucleus of a cell called?

The spherical body found in the nucleus of a cell is known as the nucleolus. This structure is primarily involved in the production and assembly of ribosomes, which are essential for protein synthesis in the cell. The nucleolus is not a separate organelle but rather a dense region within the nucleus where ribosomal RNA (rRNA) is transcribed and combined with proteins to form ribosome subunits.

The nucleolus plays a crucial role in the cell's ability to produce proteins efficiently, as ribosomes are necessary for translating messenger RNA (mRNA) into polypeptide chains. It is usually visible under a microscope as a dark-stained body within the light-stained nucleoplasm of the nucleus. This is why the identification of the nucleolus is essential for understanding cellular function and the overall biology of the cell.

The other terms mentioned, such as ribosome, nucleus, and endoplasmic reticulum, refer to different structures or components of the cell. The ribosome is the site of protein synthesis, the nucleus is the control center containing genetic material, and the endoplasmic reticulum is involved in the synthesis and transport of proteins and lipids, but none of these terms specifically denote the spherical body known as the nucleolus.