G2fase

G2fase, or the G2 phase, is the second subphase of interphase in the cell cycle of eukaryotic organisms, following DNA replication during the S phase and preceding mitosis (M phase). During G2, cells continue to grow, synthesize proteins, and produce organelles as they prepare for division. The genome has been replicated, and the cell checks for DNA damage and replication completion before entering M phase.

Regulation of the G2 phase centers on ensuring the cell is ready to divide. Entry into M phase is controlled primarily by cyclin-dependent kinases, particularly cyclin B-CDK1. DNA damage or incomplete replication activates G2 checkpoints through ATM/ATR and downstream kinases such as CHK1 and CHK2, which inhibit CDK1 activation (for example via the WEE1 kinase) and allow time for repair. If damage is irreparable, cells may undergo apoptosis or permanent arrest.

Duration and variation: The length of G2 varies by cell type, organism, and external conditions, and can be influenced by stress, nutrient availability, and overall cellular health.

Clinical and research relevance: Abnormal regulation of G2 can contribute to genomic instability and oncogenesis. The G2/M transition and the DNA damage response are subjects of study for cancer biology and are targeted by various therapeutic strategies to sensitize cells to treatment or to prevent proliferation.

Names and usage: In some languages the phase is referred to as G2-fase (for example in Dutch or German), but it denotes the same stage of the cell cycle.