order: deoxyribonucleic acid (DNA) replication (S phase) always precedes chromosome segregation (mitosis or M phase), followed by cell division (cytokinesis).
The second is that this sequence of chromosomal events repeats with a period equal to the mass doubling time (the time required to double cytoplasmic mass). The first set of constraints is necessary to maintain the integrity of the genome;
the second set is necessary to maintain the cell’s nucleocytoplasmic ratio within viable bounds.
The correct sequence of events is a robust characteristic of the chromosome cycle. If an early event is blocked, then usually none of the following events takes place, suggesting that cell cycle events form a dependent sequence. For example, if DNA replication is blocked by a drug or a conditional mutation, then later events – mitosis and cytokinesis – are not initiated. If mitosis is blocked, then cell division and the subsequent S phase will not take place.
If cell growth is blocked by nutrient deprivation or antigrowth signals, the cell cycle will arrest in G1 or G2
(depending on cell type).