Meiosis By: AJ Rivera

Meiosis I

In Meiosis I, all homologues move apart from their partners & end up in two new nuclei. When cytoplasm divides, there are 2 daughter cells with 1 of each type of chromosome. The chromosomes are still duplicated.

Meiosis I Prophase I

Chromosomes were duplicated earlier during interphase. These chromosomes then start to condense - each pairs with its homologue and swaps segments. New microtubiles are forming a bipolar spindle. One of the 2 centrosomes moves to the opposite side of the nuclear envelope which begins to break up. CROSSING over occurs here, therefore allowing for variation.

Meosis I Metaphase I

One set of microtubules has tethered one chromosome of each type of one spindle pole and another set tethered its homologue to the other spindle pole. A tug of war of sorts has aligned the chromosomes midway between the 2 spindle poles.

Meiosis I Anaphase I

One of each duplicated chromosome, maternal or paternal moves to a spindle pole while it's homologue moves to the opposite pole. Motor proteins and microtubules allow fo this movement.

Meiosis I Telophase I

One of each type of chromosome has arrived at the spindle pole. In most species, the cytoplasm divides at this time. All of the chromosomes are still duplicated.

Meiosis II

In Meiosis II, new nuclear envelopes begin to enclose them as 4 nuclei into 2 cells. Typically, 4 haploid N cells form after a 2nd cytoplasmic division.

Meiosis II Prophase II

IN EACH CELL ONE OF THE TWO CENTRIOLES MOVES TO THE OPPOSITE SIDE OF THE CELL AND A NEW BIPOLAR SPINDLE FORMS; SOME SPINDLE MICROTUBULES HARNESS ONE CHROMATID OF EACH CHROMOSOME TO A SPINDLE POLE; OTHER MICROTUBULES HARNESS ITS SISTER CHROMATID TO THE OTHER POLE

Meiosis II Metaphase II

BY NOW MICROTUBULES FROM BOTH SPINDLE POLES HAVE FINISHED A TUG OF WAR; THEY HAVE ALIGNED ALL OF THE STILL DUPLICATED CHROMOSOMES MIDWAY BETWEEN THE POLES

Meiosis II Anaphase II

THE SISTER CHROMATIDS OF EACH CHROMOSOMES MOVE APART AND ARE NOW INDIVIDUAL UNDUPLICATED CHROMOSOMES; MICROTUBULES PULL THEM TOWARD OPPOSITE SPINDLE POLES AS OTHER MICROTUBULES PUSH THE POLES APART; A PARCEL OF ONE OF EACH TYPE OF CHROMOSOME WILL END UP NEAR EACH POLE

Meiosis II Telophase II

A NEW NUCLEAR ENVELOPE ENCLOSES EACH PARCEL OF CHROMOSOMES SO THERE ARE NOW FOUR NUCLEI; THE CYTOPLASM DIVIDES; EACH OF THE DAUGHTER CELLS NOW HAS A HAPLOID (N) OF UNDUPLICATED CHROMOSOMES

Created By
AJ Rivera
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