Page 116 - Atlas of Histology with Functional Correlations

In this short phase, the chromosomes become highly condensed. The

chromosomes are aligned along the equator of the cell as a result of their
attachment to the kinetochore microtubules of the mitotic spindles that radiate
from both spindle poles. The kinetochore microtubules direct the movement of
chromosomes toward the middle of the cells, forming the metaphase or
equatorial plate (Fig. 3.1A, B).

Anaphase

During this phase, the chromatid pairs separate at the centromere because of an
enzymatic action, and each chromatid now becomes a separate chromosome.

These chromosomes now begin their migration to the opposite poles of the cell,
pulled by the shortening of the kinetochore microtubules, which are attached to
the centromeres. The migrating or pulled chromosomes exhibit a V shape in the

cell. In late anaphase, a cleavage furrow in the cell membrane appears at the cell
equator, indicating the area where the cell will divide (Fig. 3.1C).

Telophase

This is the terminal phase of mitosis. It begins when the chromosomes complete
their migration to the opposite side of the mitotic spindle and the chromosomes
decondense into the chromatin of the interphase cell. Also, the nucleolus
reappears, and the rough endoplasmic reticulum begins to form a new nuclear
envelope. A constriction of the cytoplasm is formed by the contractile ring

composed of actin filaments, which becomes the site of cleavage for the
separation of daughter cells. Cleavage of the joined daughter cells follows.
Cytokinesis is the process by which the cytoplasm is divided into two

genetically identical cells (Fig. 3.1D, E).

Interphase

Mitosis is now complete, and the cell is ready for the new interphase to begin.

The chromosomes have unraveled to become visible as chromatin material in
the nucleus. The resulting cell division has produced two new cells that are
identical in their genetic content to the parent cell (Fig. 3.1E).

MEIOSIS

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