Cell Division Visualizer — Mitosis and Meiosis
Step through all phases of mitosis (6 stages) and meiosis (4 stages) with labelled SVG diagrams. Navigate forward and back or jump to any phase. Descriptions explain the biological significance of each stage. No signup, runs entirely in your browser.
Interphase
The cell prepares for division. DNA is replicated during S phase, forming sister chromatids. The nucleus is intact and chromatin appears as loosely coiled threads. The cell grows and synthesises proteins.
Revision Tips for Cell Division
PMAT mnemonic
Remember mitosis phases with PMAT: Prophase, Metaphase, Anaphase, Telophase. In meiosis each phase gets a Roman numeral suffix (Prophase I, Metaphase I, etc.) because there are two rounds of division.
Chromosomes vs chromatids
A chromosome after replication consists of two sister chromatids joined at the centromere. In Anaphase of mitosis, sister chromatids separate and each is now called a chromosome. In Anaphase I of meiosis, homologous chromosomes separate — sister chromatids stay joined.
2n vs n
Diploid cells (2n) have two sets of chromosomes. Human diploid cells have 46 (23 pairs). Haploid cells (n) have one set — 23 chromosomes in human gametes. Fertilisation restores the diploid number.
Sources of variation
Meiosis produces variation through two mechanisms: crossing over (prophase I) exchanges segments between homologous chromosomes, and independent assortment (metaphase I) randomly assigns maternal or paternal chromosomes to each pole.
Frequently Asked Questions
What is the difference between mitosis and meiosis?
Mitosis produces two diploid (2n) daughter cells genetically identical to the parent — used for growth and repair. Meiosis produces four haploid (n) daughter cells (gametes) with half the chromosome number — used for sexual reproduction. Meiosis also introduces genetic variation through crossing over.
What happens during Prophase?
In Prophase (mitosis): chromatin condenses into visible chromosomes (each consisting of two sister chromatids joined at the centromere), the nuclear envelope breaks down, and the spindle apparatus forms from centrioles.
What is crossing over and when does it occur?
Crossing over (recombination) occurs during Prophase I of meiosis, when homologous chromosomes pair up (synapsis) and exchange segments of DNA at points called chiasmata. This shuffles allele combinations and is a major source of genetic variation.
Why does meiosis produce 4 cells but mitosis produces 2?
Meiosis involves two successive divisions: Meiosis I separates homologous chromosome pairs (reducing chromosome number by half), and Meiosis II separates sister chromatids — producing 4 haploid cells in total. Mitosis has only one division.
What is the significance of metaphase for karyotyping?
Metaphase is when chromosomes are most condensed and aligned at the cell equator. This is the ideal stage for karyotyping because individual chromosomes are most visible and easiest to photograph and count.
Is this tool suitable for A-level or GCSE revision?
Yes. The diagrams and descriptions cover the syllabus content for GCSE, A-level, IB Biology, and equivalent biology courses. The descriptions include the key vocabulary examiners expect (centromere, sister chromatids, spindle apparatus, etc.).