* Centrioles: These are small, cylindrical structures that are involved in the formation of the mitotic spindle during cell division. Centrioles replicate in the G1 phase to ensure that each daughter cell receives a complete set of centrioles.
Note: While some sources may mention that lysosomes and peroxisomes also replicate in the G1 phase, they actually grow and divide throughout the cell cycle. They are not typically considered to undergo specific replication events in G1.
The other major organelles, such as the nucleus, endoplasmic reticulum, Golgi apparatus, and mitochondria, primarily replicate in the S phase (DNA synthesis) or during other phases of the cell cycle.
