Calculate the mitotic index to determine the fraction of cells undergoing mitosis in a tissue sample
Mitotic Index
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Mitotic Fraction
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Prophase Percentage
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Metaphase Percentage
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Anaphase Percentage
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Telophase Percentage
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The mitotic index is a measure of cellular proliferation that represents the fraction or percentage of cells in a tissue sample that are actively dividing (undergoing mitosis). It's calculated by dividing the number of cells in mitosis by the total number of cells observed and multiplying by 100.
The mitotic index is calculated using the formula: MI = (M / T) × 100, where M is the number of cells in mitosis and T is the total number of cells observed. The result gives you the percentage of cells actively dividing.
Normal mitotic index values vary by tissue type and organism. In humans, typical values range from 0.5% to 3% for most tissues, though rapidly dividing tissues like bone marrow or intestinal epithelium can have higher values. Cancer tissues often show elevated mitotic indices.
Count all cells showing clear signs of mitosis: prophase (condensed chromosomes), metaphase (chromosomes aligned at the equator), anaphase (chromosomes separating), and telophase (nuclear division completing). Do not count interphase cells.
For reliable results, count at least 500-1000 cells total. Larger sample sizes provide more accurate mitotic index calculations and reduce sampling error. The exact number depends on your research requirements and the mitotic activity of your tissue.
Several factors influence mitotic index including tissue type, age of organism, time of day (circadian rhythms), growth conditions, disease states, and drug treatments. Cancer tissues typically show higher mitotic indices than normal tissues.
Yes, the mitotic index calculation formula is universal across species since it's simply a ratio of dividing cells to total cells. However, normal reference values vary significantly between different organisms and tissue types.
Mitotic index is a snapshot measurement of cells in mitosis at a specific time, while proliferation rate considers the duration of cell division. Mitotic index provides an estimate of proliferative activity but doesn't account for cell cycle length variations.