On this page
Cell division questions look like memory questions, but the marks are usually lost on counting: how many chromosomes, how many chromatids, how much DNA, at which stage. Students who can name all five stages of prophase I still mix up 2n and 4C. This post sets out the stages, tracks the numbers through one worked example, and lists the errors to watch for.
What does NEET expect?
The NEET (UG) 2026 syllabus lists "Cell division: Cell cycle, mitosis, meiosis and their significance" in the unit on cell structure and function. The content comes from NCERT's Class 11 chapter on cell cycle and cell division. Check the syllabus for your exam year when it is notified.
The cell cycle is a major research topic as well as a textbook chapter. The 2001 Nobel Prize in Physiology or Medicine went to Leland Hartwell, Tim Hunt and Paul Nurse "for their discoveries of key regulators of the cell cycle".
How is the cell cycle organised?
NCERT uses human cells in culture as the example: they divide about once every 24 hours, and the division itself takes only about an hour. Interphase takes more than 95% of the cycle. Yeast can complete a cycle in about 90 minutes.
G1: the cell grows and is metabolically active, but DNA is not replicated.
S: DNA is replicated. DNA content goes from 2C to 4C, but the chromosome number stays at 2n.
G2: proteins are made in preparation for mitosis.
M: karyokinesis (prophase, metaphase, anaphase, telophase), usually followed by cytokinesis.
G0: cells that stop dividing, such as heart cells, leave G1 and enter this quiescent stage.
Why do students lose marks here?
Research on how students understand cell division points to one root cause. Lewis, Leach and Wood-Robinson (2000) found a "widespread lack of understanding" of the physical link between chromosomes and genetic material, and of how chromosome behaviour in cell division keeps genetic information continuous. Newman, Catavero and Wright (2012) found that students usually understood basic chromosome structure but did not use that knowledge to explain processes such as homologous pairing in meiosis.
The fix is to tie every stage to what is physically happening to the chromosomes, and to count from that.
Worked example: counting through mitosis and meiosis
NCERT asks you to track onion root tip cells, which have 16 chromosomes. Count chromosomes by counting centromeres, and count DNA in units of C, where 2C is the content of a cell in G1.
Mitosis, starting from a cell with 2n = 16:
G1: 16 chromosomes, one chromatid each, 2C.
After S and in G2: still 16 chromosomes, now two sister chromatids each (32 chromatids), 4C.
Metaphase: 16 chromosomes lined up at the metaphase plate, 4C.
Anaphase: centromeres split, so 32 chromosomes move apart, 16 to each pole. The cell still holds 4C.
Each daughter cell: 16 chromosomes, 2C.
Meiosis, in a cell of the same species with 2n = 16:
After S: 16 chromosomes, 4C. Homologues pair in prophase I to form 8 bivalents.
Anaphase I: homologous chromosomes separate, but sister chromatids stay together.
After meiosis I: each cell has 8 chromosomes, each with two chromatids, 2C.
Anaphase II: centromeres split and sister chromatids separate.
After meiosis II: four cells, each with 8 chromosomes and 1C.
What happens in prophase I?
NCERT divides prophase I into five stages. Learn them as a sequence of events, not as a list of names:
Leptotene: chromosomes become visible.
Zygotene: homologous chromosomes pair (synapsis), with the synaptonemal complex. A pair is a bivalent or tetrad.
Pachytene: crossing over between non-sister chromatids, catalysed by recombinase. Recombination nodules appear.
Diplotene: the synaptonemal complex dissolves and the homologues begin to separate, except at the crossover points, the chiasmata.
Diakinesis: chiasmata terminalise and the nuclear envelope breaks down, leading into metaphase I.
There is no DNA replication in interkinesis, the short gap between meiosis I and meiosis II.
Which errors cost the most marks?
Thinking S phase doubles the chromosome number. It doubles DNA; the chromosome number stays at 2n.
Confusing anaphase I and anaphase II. Homologues separate in anaphase I; sister chromatids separate in anaphase II, as in mitosis.
Placing crossing over at the wrong stage. It happens at pachytene; chiasmata are seen at diplotene.
Counting chromatids as chromosomes at metaphase.
Forgetting the exceptions NCERT mentions, such as haploid male honey bees dividing by mitosis.
Our guide to using NCERT for NEET shows how to read chapters like this one actively.
A practice routine
Draw the table from memory (twice a week): stages down the side, chromosome number, chromatids per chromosome and DNA content across the top, for both mitosis and meiosis. Check against NCERT.
Change the starting number: redo the table for 2n = 8 and 2n = 46.
Make question cards for the five prophase I stages, with an event on one side and the stage on the other. Our post on flashcards that work explains how to use them.
Explain one stage aloud in terms of what the chromosomes are doing.
If a stage will not stay in place in your head, Fermi's Simulation Lab has interactive simulations for ideas that are easier to see than to read.
Today, without notes, fill in the counting table for a cell with 2n = 8 through both divisions, then check each row against the worked example above.
