Learning objectives
- Name and describe the stages of mitosis
- Describe the two divisions of meiosis and crossing over
- State at least five differences between mitosis and meiosis
1. Mitosis
Mitosis occurs in meristems — root tips, shoot tips and the cambium. After interphase (DNA replication), the cell passes through prophase (chromosomes condense), metaphase (chromosomes line up on the equator), anaphase (sister chromatids pulled to opposite poles) and telophase (nuclear membranes re-form).
In plants, cytokinesis happens by a cell plate forming across the middle of the cell, not by furrowing as in animal cells. Plant cells also lack centrioles.
2. Meiosis
Meiosis occurs in the anthers and ovules. Meiosis I separates homologous chromosomes (reduction division); meiosis II separates chromatids. During prophase I, homologous chromosomes pair and exchange segments (crossing over), and independent assortment at metaphase I shuffles chromosomes further.
- Mitosis: 1 division, 2 identical diploid (2n) cells
- Meiosis: 2 divisions, 4 different haploid (n) cells
- Crossing over happens only in meiosis
Key definitions
- Meristem
- A region of actively dividing undifferentiated cells, e.g. root and shoot tips.
- Crossing over
- Exchange of genetic material between homologous chromosomes during prophase I of meiosis.
- Cell plate
- The new wall that forms between daughter plant cells during cytokinesis.
Exam tips
- Use a two-column table for mitosis vs meiosis questions — it is quick to mark and earns full credit.
- Always mention where each division happens in a plant (meristem vs anther/ovule).
Practice exam questions & model answers
Q1.State four differences between mitosis and meiosis.
Mitosis has one division, meiosis two; mitosis gives two daughter cells, meiosis four; mitotic daughter cells are diploid and identical, meiotic ones haploid and genetically different; crossing over occurs only in meiosis; mitosis occurs in meristems for growth, meiosis in anthers and ovules for reproduction.
Q2.Why is meiosis important in crop improvement?
Meiosis creates new combinations of genes through crossing over and independent assortment. This genetic variation is the raw material plant breeders select from to develop higher-yielding, disease-resistant varieties.
Continue revising
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Put the theory to work — diagnose a real leaf photo or browse the disease library.