Mitosis vs Meiosis (Comparison)

NCERT grounding

NCERT Class 11 Biology, Chapter 10, builds the contrast explicitly. The M Phase of mitosis is described as the equational division because "the number of chromosomes in the parent and progeny cells is the same." Meiosis, introduced in §10.4, is "this specialised kind of cell division that reduces the chromosome number by half" — the reduction division. The summary closes the loop: "Mitosis thus, is the equational division… In contrast to mitosis, meiosis occurs in the diploid cells, which are destined to form gametes."

Mitosis vs meiosis: the full comparison

Both divisions start identically. A cell completes the S phase of interphase, doubling its DNA from 2C to 4C while the chromosome number stays unchanged — each chromosome now carries two identical sister chromatids joined at the centromere. From this shared starting point the two pathways diverge sharply. Mitosis runs a single round of karyokinesis and cytokinesis; meiosis runs two rounds without an intervening replication. That single structural difference — one division versus two on one replication — cascades into every other contrast NEET asks about.

The most fundamental distinction is equational versus reductional. Mitosis is equational: a diploid (2n) mother cell gives two diploid (2n) daughters, and a haploid mother (in some lower plants and male honey bees) gives haploid daughters. The chromosome number is conserved. Meiosis is reductional: a diploid (2n) mother cell gives four haploid (n) products. The halving happens specifically in meiosis I, where homologous chromosomes — not sister chromatids — are pulled to opposite poles. By the end of meiosis I each pole already has the haploid number; meiosis II merely separates the sister chromatids, much like a mitosis.

Synapsis, bivalents and crossing over

The defining molecular event of meiosis happens in its long, five-stage prophase I — and it has no counterpart in mitosis. During zygotene, homologous chromosomes pair up in a process called synapsis, forming a synaptonemal complex; each synapsed pair is a bivalent (tetrad). During pachytene, recombination nodules appear and crossing over — the enzyme-mediated (recombinase) exchange of segments between non-sister chromatids — takes place. As the synaptonemal complex dissolves at diplotene, the homologues stay joined at X-shaped chiasmata, which terminalise at diakinesis. Mitotic prophase has none of this: no pairing, no bivalents, no chiasmata, no crossing over. This is why NEET 2022 and NEET 2016 both asked which event "never occurs" in mitosis and answered: pairing of homologous chromosomes.

Centromere splitting — the timing trap

In mitosis the centromere splits at anaphase, so sister chromatids separate in that one and only division. In meiosis the centromere behaves differently. At anaphase I the homologous chromosomes separate while sister chromatids stay associated at their centromeres — the centromere does not split. Splitting is deferred to anaphase II, where the sister chromatids finally part. NEET 2023 and NEET 2021 both asked which meiotic stage involves division of the centromere; the answer to each was anaphase II. NCERT's exercise question 10 — "distinguish anaphase of mitosis from anaphase I of meiosis" — turns on exactly this point.

Where each division occurs, and genetic outcome

Mitosis occurs in diploid somatic and meristematic cells — the apical and lateral cambium drive lifelong plant growth, and dividing cells replace lost epidermal, gut-lining and blood cells. NCERT notes the exceptions: in some lower plants and social insects such as male honey bees, even haploid cells divide by mitosis, and plants show mitosis in both haploid and diploid cells. Meiosis is restricted to specialised diploid reproductive cells destined to form gametes — the spore mother cells of plants and germ cells of animals — occurring during gametogenesis.

The genetic outcome follows from the mechanism. Mitosis produces genetically identical clones: no pairing, no recombination, faithful equational partitioning. Meiosis produces genetically variable products through two sources — crossing over in prophase I and the independent assortment of homologues at metaphase I. This variation, NCERT stresses, is the engine of evolution.

Parameter-by-parameter table

This is the centrepiece of the page — read it as the canonical answer to NCERT exercise 11, "list the main differences between mitosis and meiosis."

Division outcomes & ploidy

Reading the two divisions as a parallel sequence makes the ploidy logic concrete. Both begin at 2n with 4C DNA after S phase. Mitosis runs four stages once; meiosis runs the same four stages twice, with the reduction occurring in the first round.

Function of each division

The two divisions answer two different biological needs. Mitosis serves the somatic life of the organism: growth of multicellular bodies, restoration of the nucleo-cytoplasmic ratio, repair and continuous replacement of epidermal, gut-lining and blood cells, and the lifelong growth of plants through meristematic divisions in the apical and lateral cambium. Meiosis serves sexual reproduction: it produces haploid gametes, and — paradoxically, while halving the number each generation — it conserves the species' chromosome number across generations, because fertilisation restores the diploid state. Crucially, it generates the genetic variation that fuels evolution.

Worked examples

Common confusion & NEET traps