MEIOSIS

G2 INTERPHASE•Nuclear envelope present•Nucleoli visible•2 centrosomes (in animal cells these contain the centrioles)•Chromosomes are long, thin, and invisible under the light microscope

PROPHASE I•Chromosomes condense•Synapsis occurs (pairing of homologous chromosomes)•Tetrads form (4 chromatids)•Crossing over occurs at chiasma•Centrosomes move apart•Spindle forms•Nuclear envelope and nucleolus disappear•Spindle attaches to kinetochore

METAPHASE I AND ANAPHASE I•Homologous chromosomes line up in pairs along the metaphase plate•Kinetochore microtubules are attached to each pair•Homologous chromosomes are pulled toward opposite poles•Chomosomes are still made of sister chromatids•Cell elongates

TELOPHASE I AND CYTOKINESIS•Each pole has a haploid set of chromosomes •Cleavage furrow/cell plate forms•Nuclear envelope and nucleolus may reform•There may be a resting phase called interkinesis•NO doubling of chromosomes happens

PROPHASE II•Spindle forms•Chromosomes condense•Nuclear envelope and nucleolus disappears•Centrosomes move apart

METAPHASE II AND ANAPHASE II•Chromosomes line up SINGLE FILE along the metaphase plate•Kinetochore microtubules are attached to sister chromatids•Centrosomes split•Chromatids are pulled to opposite poles by kinetochore microtubules•Cell elongates

TELOPHASE II AND CYTOKINESIS•Nuclei reform at opposite poles•Cytokinesis occurs•4 daughter nuclei have formed each with one half the original number of chromosomes as the parent cell•Each gamete formed is unique