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• http://highered.mcgraw-hill.com/sites/0072495855/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. • http://www.biology.arizona.edu/Cell_bio/activities/cell_cycle/cell_cycle.html

•  Mitosis Rap• http://www.nclark.net/MitosisRap.mp3  

• Mitosis Animation and Tutorialhttp://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells3.html

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

http://www.sumanasinc.com/webcontent/animations/content/mitosis.html

• Meiosis• http://www.youtube.com/watch?v=D1_-mQS_FZ0 

http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter19/animation__how_meiosis_works.html  • http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter12/animations.html#   

• Mitosis vs Meiosishttp://www.johnkyrk.com/meiosis.html

http://www.pbs.org/wgbh/nova/baby/divide.html#

http://www.pbs.org/wgbh/nova/baby/divi_flash.html

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__comparison_of_meiosis_and_mitosis__quiz_1_.html

•  

Meiosis

• like mitosis, meiosis follows Interphase and

ends with cytokenisis

• The 1st meiotic division results in two cells with ½ the number of chromosomes as the parent cell.

• The 2nd 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/0072943696/student_view0/chapter19/animation__how_meiosis_works.html

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

• http://www.biology.arizona.edu/cell_bio/tutorials/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.