CELL CYCLE AND CELL DIVISION · Comparison Tables

1. Interphase vs M Phase

Feature	Interphase	M phase
Position in cell cycle	Between two successive M phases	Actual cell division phase
Main events	Cell growth, DNA replication and orderly preparation for division	Karyokinesis followed usually by cytokinesis
Duration in a 24-hour human cell cycle	More than 95% of total duration	About one hour
Common misconception	Called resting phase, but it is metabolically active and preparatory	Most dramatic period, with major cellular reorganisation
Outcome	Genome and cellular constituents become ready for division	Two daughter cells form

2. G₁ vs S vs G₂ Phase

Feature	G₁ phase	S phase	G₂ phase
Position	Between mitosis and DNA replication	Synthesis phase	After DNA synthesis, before mitosis
DNA status	DNA not replicated; 2C in a diploid cell	DNA replicates: 2C to 4C, but chromosome number stays 2n	Replicated DNA remains 4C
Main activity	Metabolic activity and continuous cell growth	DNA replication; centriole duplicates in animal cells	Cell growth continues; proteins are synthesised for mitosis
Key point	Cells may exit here to G₀	No increase in chromosome number despite DNA doubling	Direct preparation for M phase

G₀ / quiescent stage Cells that leave G₁ remain metabolically active but do not proliferate unless required by the organism.

3. Mitosis vs Meiosis

Feature	Mitosis	Meiosis
Type of division	Equational division	Reduction division
Number of divisions	One nuclear division	Two sequential divisions (I and II) after a single DNA replication
Daughter cells	Two, usually diploid, with same chromosome number and genetic complement	Four haploid cells at the end of meiosis II
Homologous pairing / recombination	Absent	Present in prophase I; crossing over occurs between non-sister chromatids
Major role	Growth, cell repair and maintenance of nucleo-cytoplasmic ratio	Gamete formation, halving chromosome number and generating variation
Where seen	Usually diploid somatic cells	Specialised diploid cells destined to form gametes

4. Stages of Mitosis Compared

Stage	Chromosome behaviour	Other key events
Prophase	Chromatin condenses; each chromosome has two chromatids joined at centromere	Centrosomes move to opposite poles; asters and spindle form; by end, nucleolus, ER, Golgi and nuclear envelope disappear
Metaphase	Chromosomes fully condensed and align at equator on metaphase plate	Spindle fibres attach to kinetochores of sister chromatids from opposite poles
Anaphase	Centromeres split; chromatids separate as daughter chromosomes and migrate to opposite poles	Centromeres lead, arms trail behind
Telophase	Chromosomes reach poles and decondense; discrete identities disappear	Nuclear envelope, nucleolus, ER and Golgi reform, creating two daughter nuclei

5. Cytokinesis in Animal Cell vs Plant Cell

Feature	Animal cell	Plant cell
Initial event	Furrow appears in plasma membrane	Cell-plate formation begins in centre
Direction	Furrow deepens and joins at centre	New wall grows outward to meet existing lateral walls
Reason for difference	Flexible plasma membrane can constrict	Relatively inextensible cell wall prevents furrowing
Final product	Two daughter cells separated by cytoplasmic cleavage	Cell plate becomes middle lamella between two adjacent cell walls
Special case	If karyokinesis is not followed by cytokinesis, a multinucleate syncytium results; liquid endosperm in coconut is an example.

6. Substages of Prophase I

Substage	Defining event	High-yield term
Leptotene	Chromosomes gradually become visible; compaction continues	Beginning of prophase I
Zygotene	Homologous chromosomes pair	Synapsis; synaptonemal complex; paired homologues = bivalent
Pachytene	Four chromatids of each bivalent become distinct	Tetrad; recombination nodules; crossing over by recombinase
Diplotene	Synaptonemal complex dissolves; homologues begin separating except at crossover sites	Chiasmata; may last months or years in some vertebrate oocytes
Diakinesis	Chromosomes fully condense and meiotic spindle assembles	Terminalisation of chiasmata; nucleolus and nuclear envelope disappear

7. Meiosis I vs Meiosis II

Feature	Meiosis I	Meiosis II
Nature	Reductional division	Resembles normal mitosis
Prophase	Long and complex; five substages; synapsis and crossing over occur	Much simpler; nuclear membrane disappears by end
Metaphase	Bivalents align at equator; spindle attaches to homologous chromosomes	Chromosomes align at equator; spindle attaches to kinetochores of sister chromatids
Anaphase	Homologous chromosomes separate; sister chromatids remain associated	Centromeres split; sister chromatids separate
Telophase / result	Can form a dyad; interkinesis follows without DNA replication	Forms tetrad: four haploid daughter cells after cytokinesis

8. Anaphase of Mitosis vs Anaphase I vs Anaphase II

Feature	Mitosis anaphase	Meiosis I anaphase	Meiosis II anaphase
Centromere	Splits	Does not split	Splits
Structures separating	Sister chromatids	Homologous chromosomes	Sister chromatids
Chromatid association	Chromatids become daughter chromosomes	Sister chromatids stay joined at centromere	Chromatids become daughter chromosomes
Chromosome-number effect per cell	Equational: chromosome number conserved in each daughter cell	Reductional: each pole receives half the parental chromosome number	Equational within each haploid cell

Why meiosis matters Meiosis maintains species chromosome number across sexual generations and increases genetic variability, the basis for evolution.