Metaphase II
Note: Meiosis II is very similar to mitosis.
In metaphase II, the second stage of meiosis II, in each of the two daughter cells produced by the first meiotic division (which are known as secondary germ cells), the spindle again draws the chromosomes to the metaphase plate. This time, unlike metaphase I, the two kinetochores of each centromere bind to spindle fibers from opposite poles (as in mitotic metaphase). This results in separation of the sister chromatids of each chromosome during the next phase of meiosis, anaphase II.
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Compare to metaphase of mitosis >>
Compare to metaphase of meiosis I >>
A silly poem to help you remember:
Mitosis happens everywhere, even in my toe,
Meiosis only happens in my OH!
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Etymology: The name of this stage of meiosis is derived from two Greek words, meta, meaning "after," "later" or "more advanced," and phasis, meaning "stage."
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Chromosome condensation is the reorganisation of the long thin chromatin strands, of which chromosomes are composed during interphase, into compact short masses during prophase of mitosis (as well as in prophase I of meiosis). Chromosome condensation is carried out primarily by the condensin complex and occurs as the strands of DNA are tightly wrapped around histone molecules that act much like the reel of a fishing pole (see picture). If condensation did not occur as meiosis and mitosis began, the long spaghetti-like strands of the uncondensed interphase chromosomes would become hopelessly tangled like a fisherman's knot during chromosome segregation. As it is, they are neatly packed and ready for delivery to the poles!
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Mneumonic device: You can remember the first letters of each of the stages of meiosis in order by remembering one of the following three sentences:
"Peter made a tart." OR "Passed my anatomy test!" OR "Perhaps my Aunt Tillie." Take your pick.
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Meiotic arrest of oogenesis: Vertebrate eggs are arrested at the metaphase stage of meiosis II. Only upon fertilization will the metaphase-II-arrested eggs exit meiosis II and enter interphase. MORE INFORMATION >>
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