Metaphase

[1] These chromosomes, carrying genetic information, align in the equator of the cell between the spindle poles at the metaphase plate, before being separated into each of the two daughter nuclei.

[citation needed] In metaphase, microtubules from both duplicated centrosomes on opposite poles of the cell have completed attachment to kinetochores on condensed chromosomes.

[3] This even alignment is due to the counterbalance of the pulling powers generated by the opposing kinetochore microtubules,[4] analogous to a tug-of-war between two people of equal strength, ending with the destruction of B cyclin.

Any unattached or improperly attached kinetochores generate signals that prevent the activation of the anaphase promoting complex (cyclosome or APC/C), a ubiquitin ligase which targets securin and cyclin B for degradation via the proteosome.

For classical cytogenetic analyses, cells are grown in short term culture and arrested in metaphase using mitotic inhibitor.

The mitotic spindle checkpoint verifies that all the chromosomes are aligned properly on the metaphase plate and prevents premature entry into anaphase.
Chromosomes lined up on the metaphase plate. Two views with the metaphase plate rotated 60°.
Stages of early mitosis in a vertebrate cell with micrographs of chromatids
Human metaphase chromosomes (normal male karyotype )