G2 phase is the third, final, and usually the shortest subphase during interphase within the
cell cycleThe cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission...
in which the cell undergoes a period of rapid growth to prepare for mitosis. It follows successful completion of
DNA synthesisDNA synthesis commonly refers to:*DNA replication - DNA biosynthesis *Polymerase chain reaction - enzymatic DNA synthesis *Oligonucleotide synthesis - chemical synthesis of nucleic acids...
and chromosomal
replicationDNA replication, the basis for biological inheritance, is a fundamental process occurring in all living organisms to copy their DNA. This process is "semiconservative" in that each strand of the original double-stranded DNA molecule serves as template for the reproduction of the complementary strand...
during the
S phaseThe S phase, short for synthesis phase, is a period in the cell cycle during interphase, between G1 phase and the G2 phase. Following G1, the cell enters the S stage, when DNA synthesis or replication occurs. At the beginning of the S stage, each chromosome is...
, and occurs during a period of often four to five hours (for human cells). This far into interphase the nucleus is well defined, bound by a nuclear envelope and contains at least one nucleolus.
G2 phase is the third, final, and usually the shortest subphase during interphase within the
cell cycleThe cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission...
in which the cell undergoes a period of rapid growth to prepare for mitosis. It follows successful completion of
DNA synthesisDNA synthesis commonly refers to:*DNA replication - DNA biosynthesis *Polymerase chain reaction - enzymatic DNA synthesis *Oligonucleotide synthesis - chemical synthesis of nucleic acids...
and chromosomal
replicationDNA replication, the basis for biological inheritance, is a fundamental process occurring in all living organisms to copy their DNA. This process is "semiconservative" in that each strand of the original double-stranded DNA molecule serves as template for the reproduction of the complementary strand...
during the
S phaseThe S phase, short for synthesis phase, is a period in the cell cycle during interphase, between G1 phase and the G2 phase. Following G1, the cell enters the S stage, when DNA synthesis or replication occurs. At the beginning of the S stage, each chromosome is...
, and occurs during a period of often four to five hours (for human cells). This far into interphase the nucleus is well defined, bound by a nuclear envelope and contains at least one nucleolus. Although chromosomes have been replicated they cannot yet be distinguished individually because they are still in the form of loosely packed chromatin fibers. The G
2 phase prepares the cell for
mitosisMitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing...
(M phase) which is initiated by
prophaseProphase is a stage of mitosis in which the chromatin condenses into a highly ordered structure called a chromosome in which the chromatin becomes visible. Prophase accounts for approximately 3% of the cell cycle. This process, called chromatin condensation, is mediated by the condensin complex...
.
At the end of this gap phase is a
control checkpointCell cycle checkpoints are control mechanisms that ensure the fidelity of cell division in eukaryotic cells. These checkpoints verify whether the processes at each phase of the cell cycle have been accurately completed before progression into the next phase...
(G
2 checkpoint),a different
Cdk-cyclin kinasethumb|350px|Schematic of the cell cycle. outer ring: I=[[Interphase]], M=[[Mitosis]]; inner ring: M=Mitosis; G1=[[G1 phase|Growth phase 1]]; S=[[S phase|Synthesis]]; G2=[[G2 phase|Growth phase 2]]...
complex (protein kinase) termed the
M-phase promoting factor(MPF)Maturation promoting factor is a heterodimeric protein composed of cyclin B and cyclin-dependent kinase that stimulates the mitotic and meiotic cell cycles...
, to determine if the cell can proceed to enter
M phaseMitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing...
and
divideCell division is a process by which a cell, called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing...
. The G
2 checkpoint prevents cells from entering mitosis with
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
damaged since the last division, providing an opportunity for
DNA repairDNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and Radiation can cause DNA damage, resulting in as many as 1...
and stopping the proliferation of damaged cells. Because the G
2 checkpoint helps to maintain
genomicGenomics is the study of the genomes of organisms. The field includes intensive efforts to determine the entire DNA sequence of organisms and fine-scale genetic mapping efforts. The field also includes studies of intragenomic phenomena such as heterosis, epistasis, pleiotropy and other...
stability, it is an important focus in understanding the
molecular causesCarcinogenesis , is the process by which normal cells are transformed into cancer cells.Cell division is a physiological process that occurs in almost all tissues and under many circumstances...
of
cancerCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
.