Which cyclin is primarily responsible for preparing DNA for replication?

Cyclin E plays a crucial role in preparing DNA for replication. During the cell cycle, particularly in the transition from the G1 phase to the S phase, Cyclin E activates cyclin-dependent kinase 2 (CDK2). This activation initiates processes necessary for DNA replication, such as the formation of pre-replication complexes at origins of replication and the phosphorylation of proteins involved in DNA synthesis. As a result, Cyclin E effectively ensures that the cell is adequately prepared to replicate its DNA, thereby facilitating proper cell division. This makes it vital for the accurate duplication of the genome before a cell divides.