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The mitotic index is a measure of cellular proliferation. [1] It is defined as the percentage of cells undergoing mitosis in a given population of cells. Mitosis is the division of somatic cells 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.
Mitotic trigger waves are waves of Cyclin-dependent kinase 1 activity in cells that originate from pacemaker regions of the nucleus and propagate through the cytoplasm. [1]. Because trigger waves do not decrease in speed or amplitude during their propagation, they are more reliable at conveying molecular information across greater distances ...
Cells in the mitotic phase are identified by the typical appearance of their chromosomes in the cell during the mitotic phase of the cell cycle. [4] Usually the number of mitotic figures is expressed as the total number in a defined number of high power fields, such as 10 mitoses in 10 high power fields.
The major function of mitosis is to separate replicated sister chromatids, and this is accomplished in part during anaphase A when "kinetochore microtubules (or kMTs)" that link the sister chromatids to opposite spindle poles shorten by depolymerization, exerting forces on the chromatids that pull them to the poles.
The cyclins are necessary for the kinase subunit to function with the appropriate substrate. The mitotic cyclins can be grouped as cyclins A & B. These cyclins have a nine residue sequence in the N-terminal region called the “destruction box”, which can be recognized by the ubiquitin ligase enzyme which destroys the cyclins when appropriate.
In addition, when mitotic spindles are misaligned, MEN and subsequently Cdc14 are inhibited in a Bub2 and Bfa1-dependent manner to prevent degradation of mitotic cyclins and anaphase entry. [36] Sic1 is a nice example demonstrating how systems-level feedbacks interact to sense the environmental conditions and trigger cell cycle transitions.
[5] Without Cdc20, the anaphase-promoting complex (APC) cannot become activated and anaphase is not triggered. Mad2 was shown to inhibit the activity of the APC by direct physical interaction [6] in a ternary complex with Cdc20. [7] Kinetochores that remain unattached to microtubules catalyze the sequestration of Cdc20 by Mad2.
Steps of the cell cycle. The G 2-M checkpoint occurs between the G 2 and M phases. G2-M arrest. The G 2-M DNA damage checkpoint is an important cell cycle checkpoint in eukaryotic organisms that ensures that cells don't initiate mitosis until damaged or incompletely replicated DNA is sufficiently repaired.