During which phase of the cell cycle does growth and development primarily occur?

The G1 phase of the cell cycle, also known as the first gap phase, is primarily when growth and development occur. During this phase, the cell increases in size, synthesizes proteins, and produces organelles, all of which are essential for the cell to prepare for DNA replication and division. The G1 phase can also involve the cell responding to its environment, ensuring it has adequate resources and favorable conditions to proceed. This phase is crucial for cellular function and prepares the cell for the subsequent phases of the cell cycle, particularly the S phase, where DNA synthesis begins.