Category: Biology Topics Explained

Cell division is one of the most fundamental concepts in biology, and the differences between mitosis and meiosis are tested in virtually every WAEC Biology exam. If you understand these two processes clearly, you can answer questions on cell biology, genetics, reproduction, and growth — all from one foundation. What is Mitosis? Mitosis is the type of cell division that produces two daughter cells that are genetically identical to the parent cell. Each daughter cell has the same number of chromosomes as the parent cell (diploid, 2n). Where it occurs: In body cells (somatic cells) — skin, bone, muscle, liver, etc. Purpose: Growth, repair of damaged tissues, replacement of worn-out cells, and asexual reproduction. Stages of Mitosis 1. Prophase Chromosomes condense and become visible Each chromosome consists of two sister chromatids joined at the centromere The nuclear membrane begins to break down Spindle fibers start forming from the centrioles 2. Metaphase Chromosomes line up along the equator (middle) of the cell Spindle fibers attach to the centromeres of each chromosome 3. Anaphase The centromeres split Sister chromatids are pulled apart to opposite poles by the spindle fibers The cell begins to elongate 4. Telophase Chromatids arrive at opposite poles and begin to uncoil A new nuclear membrane forms around each set of chromosomes The spindle fibers disappear 5. Cytokinesis The cytoplasm divides, producing two identical daughter cells In animal cells, the membrane pinches inward (cleavage furrow) In plant cells, a cell plate forms in the middle What is Meiosis? Meiosis is the type of cell division that produces four daughter cells, each with half the number of chromosomes of the parent cell (haploid, n). The daughter cells are genetically different from each other and from the parent cell. Where it occurs: In reproductive organs — testes (to produce sperm) and ovaries (to produce eggs). Purpose: Production of gametes (sex cells) for sexual reproduction. Stages of Meiosis Meiosis involves two rounds of division — Meiosis I and Meiosis II. Meiosis I (Reduction Division): Prophase I: Homologous chromosomes pair up (synapsis) and may exchange genetic material (crossing over). This creates new combinations of genes, introducing genetic variation. Metaphase I: Homologous pairs line up at the equator. Anaphase I: Homologous chromosomes separate and move to opposite poles (this is the reduction — chromosome number is halved). Telophase I: Two cells are formed, each with half the chromosome number. Meiosis II (Similar to Mitosis): Prophase II: Chromosomes condense again. Metaphase II: Chromosomes line up at the equator. Anaphase II: Sister chromatids separate. Telophase II: Four haploid daughter cells are formed. Key Differences Between Mitosis and Meiosis FeatureMitosisMeiosisNumber of divisionsOneTwo (Meiosis I and II)Number of daughter cellsTwoFourChromosome number in daughter cellsDiploid (2n) — same as parentHaploid (n) — half of parentGenetic makeup of daughter cellsIdentical to parentDifferent from parent and each otherCrossing overDoes not occurOccurs during Prophase IPairing of homologous chromosomesDoes not occurOccurs during Prophase I (synapsis)Where it occursBody cells (somatic cells)Reproductive cells (gonads)PurposeGrowth, repair, asexual reproductionProduction of gametesRole in variationDoes not introduce variationIntroduces genetic variationExampleSkin cell division for wound healingFormation of sperm and egg cells Why This Topic Matters for WAEC WAEC tests mitosis and meiosis in multiple ways: Objective questions: "How many daughter cells does meiosis produce?" or "Crossing over occurs during which stage?" Essay questions: "Compare mitosis and meiosis" or "Describe the stages of mitosis" Application questions: "Why is meiosis important in sexual reproduction?" or "Explain how meiosis leads to genetic variation" WAEC Past Questions on This Topic Q1 (Objective): The type of cell division that results in the formation of gametes is:(a) Mitosis (b) Meiosis (c) Binary fission (d) BuddingAnswer: (b) Meiosis Q2 (Objective): Crossing over during meiosis results in:(a) Identical offspring (b) Reduced chromosome number (c) Genetic variation (d) Cell growthAnswer: (c) Genetic variation Q3 (Essay): State five differences between mitosis and meiosis.Answer: Refer to the comparison table above — any five rows will give you full marks. Watch the Video Lesson Reading about mitosis and meiosis is helpful, but watching the process happen step by step in video makes it much easier to understand and remember. 👉 Watch the full Cell Division lesson at NaijaBiologyTips.site Share this with a classmate who finds cell division confusing!