Meiosis Meiosis – germ cell go through 2 nuclear divisions that results in 4 daughter cells with half the number of chromosomes as the parent cell. –Explains how gametes are produced daughter cells are not genetically alike. –may have different combination of genes

Sexually reproducing organisms are capable of combining chromosomes from 2 parents to produce offspring. The chromosomes that combine during sexual reproduction are contained in reproductive cells called gametes.

Control of the Cell Cycle hill.com/sites/ /student_view0/chapter2/animation__control_of_the_cell_cycle.html hill.com/sites/ /student_view0/chapter2/animation__control_of_the_cell_cycle.html Activity: 25 point extra creditGo to the onion root tip activity and complete the percentages activity. Mitosis Rap Mitosis Animation and Tutorial hill.com/sites/ /student_view0/chapter2/animation__mitosis_and_cytokinesis.html hill.com/sites/ /student_view0/chapter2/animation__mitosis_and_cytokinesis.html Meiosis hill.com/sites/ /student_view0/chapter19/animation__how_meiosis_works.html hill.com/sites/ /student_view0/chapter19/animation__how_meiosis_works.html Mitosis vs Meiosis hill.com/sites/ /student_view0/chapter2/animation__comparison_of_meiosis_and_mitosis__quiz_1_.ht mlhttp://highered.mcgraw- hill.com/sites/ /student_view0/chapter2/animation__comparison_of_meiosis_and_mitosis__quiz_1_.ht ml

Meiosis like mitosis, meiosis follows Interphase and ends with cytokenisis

The 1 st meiotic division results in two cells with ½ the number of chromosomes as the parent cell. The 2 nd meiotic division is like mitosis; the number of chromosomes does not get reduced. Results in 4 daughter cells with half the # of chromosomes as the parent cell

Prophase I each chromosomes consist of two sister chromatids connected at the centromere Homologous pairs of chromosomes come together, this event is called synapsis Each pair of homologous chromosomes is called a tetrad. (4 chromatids that make up a homologous pair)

Crossing over – exchange of genes between non- sister chromatids of a homologous pair results in genetic recombination by producing a new mixture of genetic material.

Metaphase I Homologous pairs (tetrads) align in the middle of the cell.

Anaphase I homologous pairs separate and move to opposite ends of the cell. –Each chromosome consist of 2 chromatids

Telophase I Spindle fibers break down 2 new nuclei form –One around each set of chromosomes –½ the number of chromosomes as the original (parent) cells –End of Meiosis I

Meiosis II

Prophase II Spindle fibers form

Metaphase II chromosomes line up at the equator

Anaphase II sister chromatids separate at the centromere and move to opposite poles ttp://highered.mcgraw- hill.com/sites/ /student_view0/c hapter19/animation__how_meiosis_works.h tml

Telophase II 4 new nuclei appear; one around each set of chromosomes followed by cytokenesis

end up with 4 cells that are all haploid with only 1 chromatid for each chromosome

Review orials/meiosis/problems.htmlhttp:// orials/meiosis/problems.html

Meiosis - Males

Meiosis in Females

Meiosis II prophase II: spindle fibers attach to the duplicated chromosomes and begin moving them to the spindle equator. metaphase II: chromosomes align at the cell equator with one chromatid facing one pole and the other chromatid facing the opposite pole. anaphase II: the chromatids separate and are now called chromosomes. The chromosomes migrate toward the two poles. telophase II: the chromosomes arrive at the opposite poles, and the cytoplasm divides. The two meiotic divisions result in four haploid cells.