Meiosis

Front 1

Interphase

Back 1

Like mitosis, Meiosis is preceded by an interphase, during which the chromosomes duplicate. At the end of this interphase, each chromosome consists of two genetically identical sister chromatids attached together. But at this stage the chromosomes are not yet visible under the microscope except as a mass of chromatin. The cell's centrosome has also duplicated by the end of this interphase.

Front 2

Prophase

Back 2

Prophase I occurs over 90% of division time. Early in this phase, the chromatin coils up, so that individual chromosomes become visible with the microscope. In synapsis, homologous chromosomes, each composed of 2 sister chromatids, come together as pairs. The resulting structure of four chromatids is called a tetrad. Chromosomes condense further as the nucleoli disappear. Now the centrosomes more away from each other and a spindle forms btw them. Nuclear envelope breaks into fragments and the chromosome tetrads are moved towards center of cell by spindles.

Front 3

Metaphase I

Back 3

Chromosome tetrads are aligned on metaphase plate, midway btw spindles. Each chromosome is condensed thick with sister chromatids attatched at their centromeres. Spindle microtubules are attached to kinetochores at the centromeres. Homologous chromosomes of each tetrad are poised to move toward opposite poles of the cell.

Front 4

Anaphase I

Back 4

Marked by the migration of chromosomes toward the 2 poles of the cell. Sister chromatids remain attached at their centromeres unlike in mitoisis. Only tetrads split up.

Front 5

Telophase I and Cytokinesis

Back 5

Telophase- chromosomes arrive at poles of cells. Each pole has a haploid chromosome set. In some organisms chromosomes uncoil and unclear envelope re-forms and there is an interphase before Meiosis II. (no chromosome duplictation).

Front 6

Meiosis II- Prophase II, Metaphase II, Anaphase II, Telophase II and Cytokinesis

Back 6

Meiosis II essentially same as mitosis.