Quick revision – main differences between meiosis I and II?
Hello, can someone list the most important differences between meiosis I and meiosis II? I keep mixing them up for the exam. Especially what happens to chromosomes in each phase. Thanks a lot!
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Sure! The easiest way is to remember that meiosis I separates homologous chromosomes while meiosis II separates sister chromatids. Detailed breakdown available here: phases of meiosis
Meiosis I:
Starts with replicated chromosomes (each has 2 chromatids)
Homologous pairs form and crossing over happens in prophase I
Homologous chromosomes line up in pairs (metaphase I)
Whole homologous chromosomes move to opposite poles (anaphase I)
Result: two haploid cells, each chromosome still has 2 chromatids
Meiosis II:
No more crossing over or pairing of homologues
Chromosomes (still with 2 chromatids) line up singly (metaphase II)
Sister chromatids separate (anaphase II)
Result: four haploid cells with single chromatids each
So meiosis I reduces chromosome number, meiosis II is like mitosis but on already haploid cells.