DNA content and chromosome number: count the stage, then the cell
DNA can double while chromosome number stays the same. Start by saying exactly what you are counting.
This guide uses a diploid starting cell with 2n chromosomes and 2C DNA. It explains NCERT cell biology; it does not predict a 2027 question or paper pattern. The questions below are original practice examples, not past-paper questions or verified question-bank correction records.
Keep the two quantities separate
n denotes the haploid chromosome complement; C denotes the DNA amount in an unreplicated haploid complement. A replicated chromosome has sister chromatids joined at the centromere. DNA replication changes DNA amount, not the chromosome count at that stage. NCERT section 10.1.1, printed page 121 (PDF page 2) and section 10.2.2, printed page 123 (PDF page 4).
Count chromosomes by their centromeres. After sister chromatids separate, count them as daughter chromosomes. Before reading an answer, decide whether the question means the whole cell, one pole or one daughter cell. Section 10.2.3, anaphase.
The stage table
These counts are derived from the cited replication and separation events. The table assumes the usual sequence of replication, division and cytokinesis, without an extra replication round. Scroll the table sideways on a narrow screen.
| Stage | Counting unit | Chromosomes | DNA | NCERT |
|---|---|---|---|---|
| G1, before DNA replication | One diploid cell | 2n | 2C | Read |
| After S phase / G2 | One cell | 2n | 4C | Read |
| Mitotic metaphase | One cell | 2n | 4C | Read |
| Mitotic anaphase, before cytokinesis | Whole undivided cell | 4n | 4C | Read |
| Mitotic anaphase | One pole’s allocation | 2n | 2C | Read |
| After mitosis and cytokinesis | Each daughter cell | 2n | 2C | Read |
| Meiotic prophase I / metaphase I | One cell after replication | 2n | 4C | Read |
| After meiosis I and cytokinesis | Each daughter cell | n | 2C | Read |
| Metaphase II | Each cell | n | 2C | Read |
| Anaphase II, before cytokinesis | Whole cell in that division | 2n | 2C | Read |
| After meiosis II and cytokinesis | Each daughter cell | n | 1C | Read |
Do not call the whole anaphase cell tetraploid just because this table counts 4n daughter chromosomes across it. Here, 4n is a transient count across both separating groups, not a new stable ploidy state. Each future daughter receives 2n and 2C. This is the counting consequence of the separation described in section 10.2.3.
Why meiosis changes the result
Homologous chromosomes separate in meiosis I while sister chromatids remain together. There is no DNA replication during interkinesis. Sister chromatids separate in meiosis II. NCERT sections 10.4.1–10.4.2, printed page 127 (PDF page 8). That is why a daughter after meiosis I is n, 2C, but a daughter after meiosis II is n, 1C.
Check the idea before looking at the answer
For these original examples, assume a starting diploid cell with 2n = 6. Explain the counting unit as well as the number.
After replication
A cell has finished S phase but has not divided. How many chromosomes does it contain, and what is its DNA amount?
Show answer: after S phase
6 chromosomes; 4C DNA. The chromosome count remains 2n while the DNA amount doubles. Section 10.1.1.
During mitotic anaphase
Count all daughter chromosomes in the undivided cell, then count the allocation to one pole.
Show answer: whole cell versus one pole
Whole cell: 12 chromosomes and 4C DNA. One pole’s allocation: 6 chromosomes and 2C DNA. Separation changes how chromosomes are counted; no DNA replication occurs here. Derived from section 10.2.3.
After the first meiotic division
How many chromosomes and how much DNA are in each daughter after meiosis I and cytokinesis?
Show answer: after meiosis I
3 chromosomes; 2C DNA. Homologues have separated, but sister chromatids are still paired. Section 10.4.1.
After the second meiotic division
How many chromosomes and how much DNA are in each final daughter after meiosis II and cytokinesis?
Show answer: after meiosis II
3 chromosomes; 1C DNA. Sister chromatids have separated and the final daughter is haploid. Section 10.4.2 and telophase II, printed page 128 (PDF page 9).
Read and check the source
NCERT Biology, Class XI, Cell Cycle and Cell Division, chapter 10, 2026–27 reprint: replication, mitotic separation, meiosis I and II and final daughter cells. Page-specific links refer to the chapter PDF.
Source inspected from the saved NCERT 2026–27 reprint. The live chapter PDF could not be refreshed on 12 September 2026: the web fetch timed out and a direct retry was reset. The explanation is tied to that saved edition.
Take the distinction into practice
If you mixed up the counting unit, put that exact error in your mistake notebook. Then open the NeetZen web mock and choose a paper. Apply the same habit: identify what is being counted before selecting an answer. A particular paper is not promised to contain this topic.
Open the free web mock