The number of chromosomes during mitosis remains constant throughout the process, although their appearance changes. In humans, there are 46 chromosomes present during mitosis.
Here's a breakdown of what happens to the chromosomes during mitosis:
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Before Mitosis (Interphase): During the S phase of interphase, each of the 46 chromosomes duplicates. This results in 46 chromosomes, each consisting of two identical sister chromatids attached at the centromere. The number of chromosomes is still considered 46, even though the amount of DNA has doubled.
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During Mitosis: Throughout the different phases of mitosis (prophase, metaphase, anaphase, and telophase), the cell manages and separates these replicated chromosomes. At anaphase, the sister chromatids separate, and each chromatid is now considered an individual chromosome. After this separation the chromosome number briefly doubles to 92, as each sister chromatid becomes a chromosome that will be distributed to each daughter cell. Finally during telophase and cytokinesis, each daughter cell ends up with the normal number of 46 chromosomes.
To summarize:
| Stage | Chromosome Number (Human) | Description |
| ----------- | ------------------------- | ------------------------------------------------------------------------------------- |
| Interphase | 46 | Chromosomes are duplicated, each consisting of two sister chromatids. |
| Mitosis (Prophase, Metaphase) | 46 | Chromosomes (each with two sister chromatids) condense and align. |
| Mitosis (Anaphase) | Temporarily 92 briefly, then 46 per daughter cell | Sister chromatids separate, effectively doubling the chromosome count temporarily. |
| Daughter Cells (after Cytokinesis) | 46 | Each daughter cell receives 46 chromosomes. |
Therefore, while the chromosomes duplicate before mitosis, and the sister chromatids separate during anaphase, each daughter cell formed at the end has the original, unchanged number of 46 chromosomes.
