Which organelle is responsible for the growth and reproduction of a cell?

The nucleus is the organelle primarily responsible for the growth and reproduction of a cell. It contains the cell's genetic material (DNA) which carries the instructions necessary for cellular functions and the processes of growth, repair, and reproduction. During cell division, the DNA within the nucleus is replicated, ensuring that each new daughter cell receives a complete set of genetic information. This central role in managing the cell's hereditary information makes the nucleus essential for both growth and reproduction processes.

In contrast, ribosomes are involved in protein synthesis, while the nucleolus, found within the nucleus, plays a key role in assembling ribosomal RNA, which is vital for creating proteins but does not directly manage cell growth or reproduction. The endoplasmic reticulum is associated with the synthesis of proteins and lipids, contributing to cell function but not governing the cell’s growth and reproductive activities directly.