Mitosis — Revision Notes

⚡ 30-Second Revision

Interphase: — G1 (growth), S (DNA replication, 2C to 4C DNA), G2 (growth, preparation).
Prophase: — Chromatin condenses, nucleolus disappears, nuclear envelope breaks down, spindle forms.
Metaphase: — Chromosomes align at equatorial plate, kinetochores attach to spindle fibers.
Anaphase: — Centromeres split, sister chromatids separate (now daughter chromosomes), move to opposite poles.
Telophase: — Chromosomes decondense, nuclear envelope reforms, nucleolus reappears, spindle disassembles.
Cytokinesis: — Cytoplasm divides (cleavage furrow in animals, cell plate in plants).
Outcome: — Two genetically identical diploid (2n) daughter cells.
DNA Content (C value): — G1=2C, G2/Pro/Meta=4C, Ana=4C (total), Telo/Daughter=2C.
Chromosome Number (n value): — G1/G2/Pro/Meta=2n, Ana=4n (temporarily), Telo/Daughter=2n.

2-Minute Revision

Mitosis is the process of somatic cell division, yielding two genetically identical daughter cells from a single parent cell. It's vital for growth, repair, and asexual reproduction. The cell cycle begins with Interphase (G1, S, G2), where DNA replicates (doubling DNA content from 2C to 4C) and the cell grows.

Mitosis itself, or M-phase, comprises karyokinesis (nuclear division) and cytokinesis (cytoplasmic division). Karyokinesis has four phases: Prophase sees chromatin condense, nucleolus disappear, and nuclear envelope break down.

In Metaphase, chromosomes align at the equatorial plate. Anaphase is marked by centromere splitting and sister chromatids separating to opposite poles. Telophase reverses prophase events: chromosomes decondense, nuclear envelopes reform, and nucleoli reappear.

Finally, cytokinesis divides the cytoplasm, forming two distinct cells. Animal cells use a cleavage furrow, while plant cells form a cell plate. The result is two diploid cells, each with the same chromosome number and genetic information as the parent cell.

5-Minute Revision

Mitosis is the process of equational cell division, producing two daughter cells genetically identical to the parent cell. This fundamental process underpins growth, tissue repair, and asexual reproduction in eukaryotes. The entire process is part of the larger cell cycle, specifically the M-phase, which is preceded by Interphase (G1, S, G2 phases).

Interphase: This preparatory stage involves cell growth (G1), DNA replication (S-phase, where DNA content doubles from 2C to 4C, but chromosome number remains 2n as sister chromatids are still joined), and further growth and preparation for division (G2).

Karyokinesis (Nuclear Division):

1
Prophase: — The longest mitotic phase. Chromatin condenses into visible chromosomes (each with two sister chromatids). The nucleolus disappears, and the nuclear envelope begins to disintegrate. In animal cells, centrioles move to opposite poles, forming the mitotic spindle.
2
Metaphase: — The nuclear envelope completely disappears. Chromosomes become maximally condensed and align precisely at the equatorial plate (metaphase plate). Each sister chromatid is attached to spindle fibers from opposite poles via its kinetochore.
3
Anaphase: — The shortest phase. Centromeres split, separating sister chromatids. These newly separated chromatids are now considered individual daughter chromosomes. Spindle fibers shorten, pulling these daughter chromosomes to opposite poles. Temporarily, the chromosome number at the poles doubles (e.g., from 2n to 4n before cytokinesis).
4
Telophase: — Essentially the reverse of prophase. Daughter chromosomes arrive at the poles and begin to decondense. New nuclear envelopes form around each set of chromosomes, and nucleoli reappear. The spindle apparatus disassembles.

Cytokinesis (Cytoplasmic Division): This usually overlaps with telophase. In animal cells, a contractile ring forms a cleavage furrow, pinching the cell into two. In plant cells, a cell plate forms in the middle, growing outwards to divide the cell. The final outcome is two diploid daughter cells, each with 2n chromosomes and 2C DNA content, identical to the parent cell in G1.

Prelims Revision Notes

Mitosis is equational division, producing two genetically identical diploid daughter cells. It's crucial for growth, repair, and asexual reproduction.

Cell Cycle Overview:

Interphase: — G1 (growth, 2n, 2C) -> S (DNA synthesis, 2n, 4C) -> G2 (growth, 2n, 4C).
M-phase: — Karyokinesis (nuclear division) + Cytokinesis (cytoplasmic division).

Karyokinesis Phases:

1
Prophase:

* Chromatin condenses into visible chromosomes (each with 2 sister chromatids). * Nucleolus disappears. * Nuclear envelope disintegrates. * Centrioles move to poles (animal cells), spindle fibers form.

1
Metaphase:

* Chromosomes align at the equatorial plate (metaphase plate). * Kinetochores of sister chromatids attach to spindle fibers from opposite poles. * Chromosomes are maximally condensed.

1
Anaphase:

* Centromeres split, separating sister chromatids. * Sister chromatids (now daughter chromosomes) move to opposite poles. * Cell elongates. * Chromosome number temporarily doubles at each pole (e.g., 2n becomes 4n in total before cytokinesis).

1
Telophase:

* Daughter chromosomes decondense at poles. * New nuclear envelopes form around each set of chromosomes. * Nucleoli reappear. * Spindle fibers disappear.

Cytokinesis:

Animal cells: — Cleavage furrow formation (contractile ring of actin/myosin).
Plant cells: — Cell plate formation (vesicles from Golgi fuse).

Outcome: Two diploid (2n) daughter cells, each with 2C DNA content, genetically identical to the parent cell.

Key Differences from Meiosis (for quick recall):

Mitosis: 1 division, 2 identical diploid cells, no crossing over, somatic cells.
Meiosis: 2 divisions, 4 different haploid cells, crossing over, germ cells.

Vyyuha Quick Recall

To remember the phases of mitosis in order: Please Make A Tasty Curry.

Prophase
Metaphase
Anaphase
Telophase
Cytokinesis