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Biology
Explore Mitosis and Meiosis
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Drive the division process, track chromosomes and compare the outcomes of mitosis with meiosis.
Before DNA replication. Step 1 / 8.
B · father · solid lineM · mother · dashed line
Nuclear envelopeCentromere
Changing the initial diploid chromosome number resets the simulation to the first step.
Pause
1/8: Before DNA replication
Not startedFinal outcome
A diploid cell carrying unreplicated chromosomes.
- Cell count
- 1
- In each cell
- 2n = 4
- Chromosomes / cell
- 4
- Chromatids / cellⓘ
- 4
- DNA / cell
- 2C
- Structure separating now
- Not started
Conceptual milestone
The chromosome number is determined by the number of centromeres. A replicated chromosome is still one chromosome while two sister chromatids share a centromere. After the centromere splits, each chromatid becomes an independent chromosome; the chromatid/DNA-molecule index reflects the number of DNA molecules originating from chromatids by the model's convention.
Viewing stage: 4 Chromosomes / cell
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Chọn một nhiễm sắc thể trong mô hình để bật theo dõi.
Select a chromosome directly in the model to track its parental origin and homologous chromosome.
Glossary
Glossary
- Chromosome
- The unit counted by centromere; it may consist of one or two chromatids.
- Chromatid
- Each copy of a replicated chromosome; two sister chromatids remain attached at the centromere. After the centromere splits, each chromatid becomes an independent chromosome; the model keeps tracking its DNA-molecule origin.
- Homologous chromosomes
- The two chromosomes of a pair, with matching size and gene positions, one from the father and one from the mother.
Model notes
- The educational model uses cells with 2n = 2, 4 or 6 instead of the full human chromosome set.
- Shape, spacing and stage duration are adjusted for easier observation, not to true cell scale.
- Mutations, nondisjunction, spindle errors or specialized gamete formation are not simulated.
- The two mitotic cells are treated as having equivalent genetic material; the model ignores mutations and copying errors.
- Crossing over is illustrated with one segment on one homologous pair to clarify parental origin.
- Chromosome positions are rearranged for easier observation and do not reflect fixed positions in the nucleus.