12 Biology by BISM Academy
8 – Metaphase 1
Metaphase I.
Nuclear membrane disorganizes at the beginning of this phase. Spindle fibers originate and the kinetochore fibers attach to the kinetochore of homologous chromosome from each pole and arrange bivalents at the equator. The sister chromatids of individual chromosome in bivalent behave as a unit.
Anaphase I.
The kinetochore fibers contract and the spindle or pole fibers elongate, which pull the individual chromosome (each having two chromatids) towards their respective poles. It may be noted here that in contrast to anaphase of mitosis, sister chromatids are not separated. This is actually reduction phase because each pole receives half of the total number of chromosomes.
Telophase I,
Nuclear membrane reorganizes around each set of chromosomes at two poles, nucleoli reappear thus two nuclei each with half number of chromosomes are formed, later on cytoplasm divides thus terminating the first meiotic division. It is also to be noted that chromosomes may decondense during this stage.
Meiosis II.
Unlike Mitosis. After telophase I two daughter cells experience small interphase, but in contrast to interphase of mitosis there is no replication of chromosomes. Just like Mitosis.
Prophase II, metaphase II, anaphase II and telophase II are just like the respective phases of mitosis during which
the chromosomes, condense,
mitotic apparatus forms,
chromosomes arrange at the equator
individual/sister chromatids move apart, and
ultimately four nuclei at the respective poles of two daughter cells (formed after meiosis I) are formed.
Cytokinesis.
It takes place and four haploid cells, with half of the number of chromosomes (chromatids) are formed