3B Scientific Cell Division II Chart, Meiosis - Manual (Page 7)

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Meiosis
Meiotic division II
The second meiotic division occurs just like mitosis (usual nuclear and cell division). It is therefore also
referred to as equational division. Since the chromosomes were not duplicated again during the preceding
interkinesis, the second meiotic division, which now follows, includes the reduction of the genetic informa-
tion to the haploid chromosome complement.
Prophase II
Prophase II is mostly like the prophase of mitosis and occurs very quickly in all organisms. The permeability
of the cell surface increases to allow the intake of surrounding liquids. The microtubule apparatus of the
cytoskeleton is reorganized. The nuclear membrane dissolves and the spindle is built up by rearranging
microtubules.
Metaphase II
In metaphase II, the chromosomes are once more arranged at the equator level and the two ends of the
spindle are located at the two opposite poles (as in metaphase I). A major difference to metaphase I is that
two kinetochores have developed at the sister chromatids which in this case point to opposite pole directions.
9. Anaphase II
During anaphase II, following now, the two sister chromatids (1) of each chromosome are disjoined just as
in mitosis.
The separation begins at the kinetochores (2), the point where the traction fibres of the central spindle
are attached. From here, the chromosomes are pulled slowly towards the centrioles (4) located at the cell
poles, moving along the microtubules (3) which create a traction effect as they become shorter. The micro-
tubules (5) that are not connected to chromatids now become longer, thus increasing the distance between
the centrioles and elongating the cell. At the equator level, the beginning stage of a cleavage furrow (6)
becomes visible.
10. Telophase II and Cytokinesis II
The cleavage and division of the two cells produced during the first meiotic division now results in the pro-
duction of four haploid cells (1) with different genetic combinations resulting from random chromosome
distribution and crossing over. This explains why siblings are not identical: one child has more features
from the father, the other more from the mother. It is also possible for features of the ancestors to reappear.
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