Mitosis and Meiosis: Differences, Reduction Division and Significance (ICSE Class 10)
Updated 15 October 2026 · Fact-checked
Mitosis is one division of a body cell giving two identical diploid cells, used for growth and repair. Meiosis happens in reproductive cells: two divisions give four haploid gametes with half the chromosome number, so it is called reduction division. Crossing over between homologous chromosomes in meiosis creates variation.
Understand Mitosis and Meiosis: Differences and Significance
Two kinds of division, two jobs. A body grows and repairs itself by mitosis; it makes gametes by meiosis. The ICSE syllabus wants the stages of mitosis, but only a basic understanding of meiosis as a reduction division (stages of meiosis are not required), a brief idea of homologous chromosomes and crossing over, and the significance and differences of the two.
Diploid and haploid. A body cell has two sets of chromosomes, one set from each parent: the diploid (2n) number (46 in humans). A gamete (sperm or ovum) has one set: the haploid (n) number (23 in humans).
Homologous chromosomes. The two chromosomes of a pair, one from the father and one from the mother, are alike in length, shape and centromere position, and carry genes for the same characters at the same positions (loci). Humans have 23 such pairs. (The genes may be the same or different forms: for example, one homologue may carry the allele for tallness and the other for dwarfness.)
Meiosis as a reduction division.
- Occurs in reproductive (germ) cells: in the testes and ovaries of animals, and in anthers and ovules of flowering plants.
- DNA is copied once, but the cell divides twice (meiosis I and meiosis II).
- One diploid cell gives four haploid cells.
- Homologous chromosomes pair up and then separate, so each gamete receives one chromosome of every pair: the number is halved (2n → n). That is why meiosis is called reduction division.
- At fertilisation a haploid sperm fuses with a haploid ovum, restoring the diploid number in the zygote (n + n → 2n). Without meiosis the chromosome number would double in every generation.
Crossing over. While homologous chromosomes are paired in meiosis, non-sister chromatids (one from each homologue) exchange segments at points called chiasmata. The chromatids then carry new combinations of the parents' genes. Together with the random way homologues are shared among gametes, this makes every gamete genetically different, so offspring show variation. Crossing over does not happen in mitosis.
Significance of mitosis.
- Growth of a multicellular body from a single-celled zygote.
- Repair and replacement: healing of wounds; constant replacement of skin cells, cells lining the gut and blood cells.
- Asexual (vegetative) reproduction in some organisms.
- Keeps the chromosome number and genetic make-up the same in all body cells.
Significance of meiosis.
- Forms haploid gametes for sexual reproduction.
- Keeps the chromosome number constant from generation to generation.
- Produces variation through crossing over and new gene combinations, which is the raw material for evolution.
Differences (learn as a table).
| Feature | Mitosis | Meiosis |
|---|---|---|
| Cells where it occurs | somatic (body) cells | reproductive (germ) cells in gonads |
| Number of divisions | one | two |
| Daughter cells | two | four |
| Chromosome number | unchanged: 2n → 2n | halved: 2n → n |
| Pairing of homologous chromosomes | does not occur | occurs |
| Crossing over | absent | present |
| Daughter cells genetically | identical to each other and the parent | different from each other and the parent |
| Role | growth, repair, asexual reproduction | gamete formation, variation |
| Also called | equational division | reduction division |
Flow chart: why the number stays constant. Parent body cells 2n → (meiosis) → gametes n and n → (fertilisation) → zygote 2n → (mitosis) → every body cell of the child 2n.
Draw-and-label checklist: outcome of meiosis (no stages). One circle labelled 'diploid germ cell (2n = 4)' with two pairs of chromosomes (draw one of each pair shaded to show its parental origin) → arrow 'meiosis I' → two cells → arrow 'meiosis II' → four circles, each with two chromosomes, one from each pair, labelled 'haploid gametes (n = 2)'. Show at least one chromosome with a mixed shaded and plain segment to indicate crossing over.
Mitosis and Meiosis: Differences and Significance: key facts
- Chromosome numbers to remember
Human body cell 46 (2n) Human sperm or ovum 23 (n) Human zygote 46 (2n) Mitosis 2n gives 2n Meiosis 2n gives n - Gametes always carry half the body number.
- Cell output
One mitosis 2 identical diploid cells One meiosis 4 haploid cells k germ cells undergoing meiosis 4k sperms (in males) - In the female usually one functional ovum forms from each meiosis (not required in detail).
- Key terms
Homologous chromosomes a matched pair, one from each parent Crossing over exchange of segments between non-sister chromatids of homologues Chiasma point where crossing over occurs Reduction division meiosis, halves the chromosome number - Brief ideas only, as the syllabus says.
How to answer Mitosis and Meiosis: Differences and Significance questions
Questions on this topic are differences (2 marks), significance (2 marks), reasons (why called reduction division) and chromosome-number calculations (1-2 marks).
- 1For a difference, write the same feature for both divisions in one line each: 'Mitosis: two daughter cells; Meiosis: four daughter cells'. Never give unrelated points for the two sides.
- 2For a chromosome-number question, decide which cell is asked: body cell, zygote and cells formed by mitosis are 2n; gametes are n.
- 3If the body number is given, halve it for a gamete; if the gamete number is given, double it for a body cell or zygote.
- 4For 'why reduction division', give the fact (number halved, 2n → n) and the reason (homologous chromosomes separate, one of each pair to each gamete).
- 5For significance, give the outcome and its use: 'variation, which helps organisms adapt and evolve'.
Mitosis and Meiosis: Differences and Significance in real life
The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.
Why siblings are not identical
Suppose Ananya and her younger brother Rohan have the same parents, yet she has curly hair and dimples and he has straight hair and none.
Explain, using the events of meiosis, why two children of the same parents differ.
Try it first, then show the solutionSolution
- Each parent makes gametes by meiosis.
- During meiosis homologous chromosomes pair and crossing over exchanges segments between non-sister chromatids, creating new gene combinations.
- Each gamete then receives one chromosome of each pair at random, so every sperm and every ovum is genetically different.
- Ananya and Rohan developed from different sperm–ovum combinations, so they inherited different mixtures of their parents' genes.
Answer: Crossing over and random sharing of homologous chromosomes in meiosis make every gamete different, so each child gets a different set of genes (variation).
Memory hook: Meiosis shuffles the deck; each child is a new hand.
Constant chromosome number
Suppose a student argues: 'If a sperm and an egg each carried 46 chromosomes, the baby would just be stronger with 92.'
Explain what would happen over generations and how meiosis prevents it.
Try it first, then show the solutionSolution
- Fertilisation adds the chromosomes of the sperm to those of the ovum.
- If gametes were diploid (46), the zygote would have 92; its gametes would carry 92 and the next zygote 184.
- The number would double in every generation, and cells with wrong chromosome numbers do not develop normally.
- Meiosis halves the number to 23 in each gamete, so the zygote gets 23 + 23 = 46 every generation.
Answer: Chromosome numbers would double each generation; meiosis prevents this by making haploid (23) gametes so the zygote always has 46.
Memory hook: Halve before you add: n + n gives 2n.
Tricks to remember Mitosis and Meiosis: Differences and Significance
Short memory aids. Say each one aloud once, then use it on a question the same day.
MiTosis is Two; MEiosis makes Eggs (and sperms)
Mitosis: two identical cells. Meiosis: gametes, four of them.
Use it when: Quick recall of number and type of daughter cells.
Same, Same, Somatic
Mitosis gives the same number, the same genes, in somatic cells.
Use it when: Three features of mitosis for a difference table.
Cross over, cross the generations
Crossing over makes variation, and variation lets species change across generations (evolution).
Use it when: Significance of meiosis in one line.
Mitosis and Meiosis: Differences and Significance: solved examples
Ordered from board level to HOTS. Try each one before you open the solution.
Example 1: Gorilla-style count · 2 marks · Short answerBoard level
The body cells of a rabbit contain 44 chromosomes. How many chromosomes will there be in (a) a sperm of the rabbit, (b) a zygote, (c) a skin cell formed by mitosis? (A similar question on the sperm of a gorilla was asked in 2024.)
Try it first, then show the solutionSolution
- (a) Sperms are formed by meiosis, which halves the number: 44 ÷ 2 = 22 (1 mark).
- (b) Zygote: 22 + 22 = 44; (c) mitosis keeps the number: 44 (1 mark).
Answer: (a) 22 (b) 44 (c) 44.
Example 2: Reduction division · 2 marks · Short answerBoard level
Why is meiosis called a reduction division? State its significance in sexual reproduction.
Try it first, then show the solutionSolution
- In meiosis homologous chromosomes separate, so each of the four daughter cells receives only one chromosome of every pair; the number is halved from 2n to n (1 mark).
- Fusion of two haploid gametes at fertilisation restores 2n in the zygote, so the chromosome number stays constant from generation to generation (1 mark).
Answer: It halves the chromosome number (2n → n); this keeps the species' number constant after fertilisation.
Example 3: Three differences · 3 marks · Short answerHarder board level
Give three differences between mitosis and meiosis with reference to (a) number of daughter cells, (b) crossing over, (c) genetic make-up of daughter cells.
Try it first, then show the solutionSolution
- (a) Mitosis: two daughter cells; meiosis: four daughter cells (1 mark).
- (b) Mitosis: no crossing over; meiosis: crossing over between non-sister chromatids of homologous chromosomes (1 mark).
- (c) Mitosis: daughter cells identical to the parent; meiosis: daughter cells genetically different from the parent and from each other (1 mark).
Answer: Two vs four cells; no crossing over vs crossing over; identical vs different daughter cells.
Example 4: Which division? · 3 marks · Short answerHarder board level
Name the type of cell division that occurs in each case and give a reason: (a) formation of pollen grains in an anther, (b) healing of a cut on the finger, (c) growth of a root tip.
Try it first, then show the solutionSolution
- (a) Meiosis, because pollen grains are haploid reproductive structures formed from diploid mother cells (1 mark).
- (b) Mitosis, because new skin cells must be identical to the old ones (1 mark).
- (c) Mitosis, because growth adds identical body cells in the meristem (1 mark).
Answer: (a) Meiosis (b) Mitosis (c) Mitosis.
Example 5: Counting gametes · 3 marks · Short answerHOTS / competency
Suppose 25 germ cells in a testis each complete meiosis. (a) How many sperms are formed? (b) If each germ cell has 2n = 8, how many chromosomes does each sperm have? (c) How many sperms would carry exactly the same combination of genes as the germ cell?
Try it first, then show the solutionSolution
- (a) Each meiosis gives four cells: 25 × 4 = 100 sperms (1 mark).
- (b) Halved: 8 ÷ 2 = 4 chromosomes (1 mark).
- (c) None: each sperm is haploid (it has only one of each pair) and crossing over has mixed the genes, so no sperm has the germ cell's full diploid combination (1 mark).
Answer: (a) 100 (b) 4 (c) None.
Example 6: A cell without meiosis · 3 marks · Case-basedHOTS / competency
Suppose a species of plant reproduces only by cuttings (asexually). A disease appears that kills plants of a particular genetic type. Explain why the whole population of this plant is at greater risk than a population of a related plant that reproduces sexually.
Try it first, then show the solutionSolution
- Cuttings grow by mitosis, which copies the parent's genes exactly, so all the plants are genetically identical (1 mark).
- If the disease kills that genetic type, every plant is equally likely to die (1 mark).
- The sexually reproducing plant forms gametes by meiosis, whose crossing over and random sharing produce variation; some individuals are likely to resist the disease and survive (1 mark).
Answer: Mitosis gives no variation, so all the clones are equally susceptible; meiosis produces variation, so some sexually produced plants may survive.
Where students lose marks in Mitosis and Meiosis: Differences and Significance
The slips examiners see most often, and what to write instead.
Mistake: Confusing body-cell and gamete numbers
CISCE examiners' comments (2024): candidates confused the chromosome numbers in body cells and gametes when asked how many chromosomes the sperms of an animal would have.
Wrong working
Body cell 40, so each sperm has 40.
Right working
Sperms are formed by meiosis: 40 ÷ 2 = 20.
Do this: Gametes are n; everything else (body cells, zygote) is 2n.
Usually costs: 1 mark.
Mistake: Unmatched differences
A difference scores only when both sides refer to the same feature.
Wrong working
Mitosis: two cells. Meiosis: crossing over.
Right working
Mitosis: two daughter cells. Meiosis: four daughter cells.
Do this: Name the feature first, then give it for both.
Usually costs: 1 mark per difference.
Mistake: Writing the stages of meiosis
The 2027 syllabus says stages of meiosis are not required; describing them wastes time and gains nothing.
Do this: Describe meiosis by its outcome: two divisions, four haploid, varied cells.
Usually costs: Time, and marks lost elsewhere.
Mistake: Saying crossing over is between sister chromatids
Sister chromatids are identical copies; exchanging pieces between them would create nothing new.
Do this: Crossing over is between non-sister chromatids of homologous chromosomes.
Usually costs: 1 mark.
Exam tips
- Use the words reduction division, haploid, diploid and homologous chromosomes exactly.
- Learn at least five lines of the difference table, each with a named feature.
- In numericals, label your answer: 'sperm (n) = 24'.
- For significance of meiosis, always include both constant chromosome number and variation.
- Keep crossing over brief: who exchanges (non-sister chromatids), when (meiosis), result (variation).
Practice questions on Mitosis and Meiosis: Differences and Significance
Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.
Q1 · 1 mark · MCQBoard level
The type of cell division in which four haploid cells are formed is:
(a) Mitosis (b) Meiosis (c) Cytokinesis (d) KaryokinesisHint
Reduction division.
Answer
(b) Meiosis.
Q2 · 1 mark · Very short answerBoard level
Define homologous chromosomes.
Hint
One from each parent.
Answer
A pair of chromosomes, one from each parent, alike in size, shape and centromere position, and carrying genes for the same characters at the same loci.
Q3 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Crossing over leads to variation.
Reason (R): Crossing over takes place between sister chromatids of the same chromosome.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.Hint
Sister or non-sister?
Answer
(c): crossing over is between non-sister chromatids of homologous chromosomes.
Q4 · 2 marks · Short answerHarder board level
The ovum of a dog has 39 chromosomes. How many chromosomes are present in (a) a cell of its liver, (b) its sperm?
Hint
Ovum is n.
Answer
(a) 2n = 78. (b) n = 39.
Q5 · 2 marks · Short answerHarder board level
Give two reasons why meiosis is essential for organisms that reproduce sexually.
Hint
Number and variation.
Answer
It halves the chromosome number in gametes so that fertilisation restores, not doubles, the diploid number; and crossing over and random sharing of homologues produce variation in the offspring.
Q6 · 2 marks · Short answerHarder board level
Where in the human body does meiosis take place? Why does it not take place in the cells of the liver?
Hint
Gonads; liver cells are somatic.
Answer
In the testes (forming sperms) and ovaries (forming ova). Liver cells are somatic cells that only need to grow and repair the organ with identical cells, which is done by mitosis; they do not form gametes.
Q7 · 3 marks · Case-basedHOTS / competency
Suppose a scientist finds a cell in an animal with 2n = 12 that, after division, has produced four cells with 6 chromosomes each, all genetically different. (a) Name the division. (b) In which organ was the cell probably located? (c) Name the event responsible for the genetic difference.
Hint
Four haploid, different cells.
Answer
(a) Meiosis. (b) A gonad (testis or ovary). (c) Crossing over between non-sister chromatids of homologous chromosomes (with random sharing of homologues).
Q8 · 2 marks · Short answerBoard level
State whether each statement is true or false and correct the false one: (a) In mitosis homologous chromosomes pair up. (b) Meiosis maintains the chromosome number from generation to generation.
Hint
Pairing is a meiosis event.
Answer
(a) False: homologous chromosomes pair up in meiosis, not in mitosis. (b) True.
Test your recall
Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.
1.How many divisions occur in meiosis?Show answer
Two.
2.How many chromosomes are there in a human ovum?Show answer
23.
3.What is the point of exchange in crossing over called?Show answer
Chiasma (plural chiasmata).
4.Which division is called equational division?Show answer
Mitosis.
5.If a gamete has 7 chromosomes, how many does the zygote have?Show answer
14.
6.Name one function of mitosis in plants.Show answer
Growth at the root and shoot tips (meristems), or vegetative reproduction.
Mitosis and Meiosis: Differences and Significance: frequently asked questions
What is the main difference between mitosis and meiosis?
Mitosis gives two identical diploid cells for growth and repair; meiosis gives four genetically different haploid cells (gametes) and halves the chromosome number.
Are the stages of meiosis in the ICSE Class 10 syllabus?
No. The 2027 syllabus asks only for a basic understanding of meiosis as a reduction division, a brief idea of homologous chromosomes and crossing over, and its significance and differences from mitosis.
What is crossing over?
The exchange of segments between non-sister chromatids of a pair of homologous chromosomes during meiosis, which produces new gene combinations and variation.
Why does the chromosome number not double after fertilisation?
Because each gamete is haploid (n), made by meiosis; two haploid gametes together give the diploid number (2n).