Mitotic index is defined as the ratio between the number of a population's cells undergoing
mitosis
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
to its total number of cells.
Purpose
The mitotic index is a measure of cellular
proliferation
Proliferation may refer to:
Weapons
*Nuclear proliferation, the spread of nuclear weapons, material, and technology
*Chemical weapon proliferation, the spread of chemical weapons, material, and technology
* Small arms proliferation, the spread of ...
.
It is defined as the percentage of cells undergoing mitosis in a given population of cells. Mitosis is the division of
somatic cell
A somatic cell (from Ancient Greek σῶμα ''sôma'', meaning "body"), or vegetal cell, is any biological cell forming the body of a multicellular organism other than a gamete, germ cell, gametocyte or undifferentiated stem cell. Such cells compo ...
s into two daughter cells. Durations of the
cell cycle and mitosis vary in different cell types. An elevated mitotic index indicates more cells are dividing. In cancer cells, the mitotic index may be elevated compared to normal growth of tissues or cellular repair of the site of an injury. The mitotic index is therefore an important
prognostic factor predicting both overall survival and response to chemotherapy in most types of cancer. It may lose much of its predictive value for elderly populations. For example, a low mitotic index loses any prognostic value for women over 70 years old with
breast cancer.
Calculation
The mitotic index is the number of cells undergoing mitosis divided by the total number of cells.
[Edexcel practical materials created by Salters-Nuffield Advanced Biology, copyright University of York Science Education Group]
A typical figure of mitotic index includes statements like "10 mitotic figures are noted per 10 high power fields" followed by "4 mitotic figures noted per 50 high power fields."
Formula
where (P+M+A+T) is the sum of all cells in phase as
prophase,
metaphase,
anaphase and
telophase, respectively and N is total number of cells.
Examples
The fastest rate of mitosis happens in the zygote, embryo and infant stage for humans and animals because mitosis is essential for embryological development. Mitosis is also required at a higher rate to grow and repair tissue. Some examples include human lymph nodes and bone marrow. Also, skin, hair, and the cells lining the intestines (epithelial cells) have high rates of mitosis. That's because those tissues constantly need to be repaired (by the cells being replaced) or growing. Plants have higher rates of mitosis at the cells of the shoot and root tips.
References
External links
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*
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https://heimduo.org/which-tissues-have-the-highest-rate-of-mitosis/
Mitosis
Medical tests
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