Cell Cycle Phases
G1, S, G2 and M phase, quiescent stage and checkpoints. (Biology › Cell Cycle and Cell Division, NEET UG syllabus.)
What is Cell Cycle Phases?
The first growth phase of interphase, where the cell grows, synthesizes proteins and RNA, and prepares for DNA replication.
Key points
- Describe the different phases of the cell cycle (G1, S, G2, M).
- Identify the key cellular events occurring in each phase of interphase.
- Explain the significance of DNA replication during the S phase and its impact on DNA content and chromosome number.
- Understand the role and characteristics of the G0 (quiescent) phase.
Common exam trap
Confusing DNA content (C) with chromosome number (n); students often mistakenly think chromosome number doubles in S phase.
Definitions
- Term
G1 phase
- Meaning
The first growth phase of interphase, where the cell grows, synthesizes proteins and RNA, and prepares for DNA replication.
- Term
S phase
- Meaning
The synthesis phase of interphase, characterized by DNA replication, resulting in the doubling of DNA content.
- Term
G2 phase
- Meaning
The second growth phase of interphase, where the cell continues to grow and synthesizes proteins required for mitosis.
- Term
M phase
- Meaning
The mitotic phase, which includes karyokinesis (nuclear division) and cytokinesis (cytoplasmic division), leading to cell division.
- Term
G0 phase
- Meaning
A quiescent (inactive) stage where cells exit the cell cycle, remain metabolically active but do not divide or proliferate.
- Term
Cell Cycle Checkpoints
- Meaning
Regulatory mechanisms at specific points in the cell cycle that monitor internal and external conditions to ensure proper progression and prevent errors.
- Term
Cyclins
- Meaning
A family of proteins whose concentrations fluctuate during the cell cycle and activate cyclin-dependent kinases (CDKs) to regulate cell cycle progression.
- Term
Cyclin-Dependent Kinases (CDKs)
- Meaning
Enzymes that, when activated by cyclins, phosphorylate target proteins to drive the cell through different phases of the cell cycle.
Learning objectives
Describe the different phases of the cell cycle (G1, S, G2, M).
Identify the key cellular events occurring in each phase of interphase.
Explain the significance of DNA replication during the S phase and its impact on DNA content and chromosome number.
Understand the role and characteristics of the G0 (quiescent) phase.
Explain the importance of cell cycle checkpoints and their regulatory molecules (cyclins, CDKs).
Prerequisites
Basic understanding of cell structure (nucleus, cytoplasm, organelles).
Knowledge of DNA, chromosomes, and genes.
Concept of diploid (2n) and haploid (n) cells.
Common mistakes
Confusing DNA content (C) with chromosome number (n); students often mistakenly think chromosome number doubles in S phase.
Not knowing the specific events that occur in each phase (G1, S, G2).
Misunderstanding the function and importance of cell cycle checkpoints.
Forgetting the existence and significance of the G0 (quiescent) phase.
Incorrectly ordering the phases of the cell cycle.
Keywords
Cell cycle
Interphase
G1 phase
S phase
G2 phase
M phase
Mitosis
Karyokinesis
Cytokinesis
G0 phase
Quiescent stage
Checkpoints
Cyclins
CDKs
DNA replication
Chromosome number
DNA content
Practice preview
Which of the following events is unique to the S phase of the cell cycle, distinguishing it from G1 and G2 phases?…
medium
Cells that do not divide further exit the G1 phase and enter an inactive stage called the:…
easy
DNA replication takes place during which phase of the cell cycle?…
easy