MEIOSISKatie Hughes, David Suarez, Abi Lawrence, Taylor Edwards and
Katelynn Granger
Meiosis 4.2.1: State that meiosis is a reduction division
of a diploid nucleus to form haploid nuclei. Called reduction division because the daughter
cells have only half of the number of chromosomes as the parent cell
Purpose: To produce gametes to facilitate sexual reproduction
Result: Four haploid cells OVERVIEW: http://highered.mcgraw-hill.com/sites/
0072495855/student_view0/chapter28/animation__stages_of_meiosis.html
Meiosis
Spilt into 2 parts: Meiosis I
Prophase Metaphase Anaphase Telophase
Meiosis II Prophase Metaphase Anaphase Telophase
Important definitions Haploid-a cell having half the number of
chromosomes than a somatic cell Somatic cell- normal body cell gamete- sex cell (sperm or egg cell) Chiasmata-the site at which crossing
over takes place. The process of crossing over
Meiosis I Interphase
Cell growth and DNA replication (review--before meiosis I) Prophase I
Chromosomes condense Homologous chromosomes pair up and crossing over
occurs (the point of cross over is known as the chiasmata) Nuclear membrane disintegrates and the centrioles travel
to the poles of the cell
Metaphase I Microtubules form a spindle and the spindle
fibers attach to the centromeres of the chromosomes
Pairs of homologous chromosomes align along the metaphase plate
Anaphase ISpindle fibers shorten and pull paired
chromosomes in opposite directions Paired homologous chromosomes
separate and pulled to opposite poles (sides) so that each pole contains one chromosome of each pair.
Telophase I A nuclear membrane forms around the
chromosomes at each pole and chromosomes uncoil Spindle fibers disintegrate The cell undergoes cytokinesis to form two daughter
cells (two haploid cells) At the end of telophase I the cells may enter a short
interphase period or proceed directly to meiosis II DNA is not replicated
Meiosis II Mostly the same!!! Except this time it involves half the
number of chromosomes as Meiosis I Prophase II
No crossing over (chiasma) Metaphase II
SAME Anaphase II
Separation of sister chromatids, instead of homologous chromosomes Telophase II
SAME
RESULT: FOUR HAPLOID DAUGHTER CELLS.
http://www.phschool.com/science/biology_place/biocoach/meiosis/mei2ani.html
http://www.johnkyrk.com/meiosis.html
10.1.2 Outline the formation of chiasmata in the process of crossing over
Chiasmata New combinations of genes within
chromosomes are possible through this process Can occur between any non-sister chromatids During prophase I, chromatids are close
together, so parts of each chromatid overlap, break at the chiasmata and reattach to the other chromatid
Sister chromatids a, b, c and d (b and c end up as new combinations called recombinants
http://www.sumanasinc.com/
webcontent/animations/
content/independentassortment.
html
Meiosis 10.1.3 Explain how meioisis results in
an effectively infinite genetic variety in gametes through crossing over in prophase I and random orientation in metaphase I
The number of chiasmata, or points of crossing over, can differ…..infinite variety!!
Mendel’s Law of Independent Assortment
10.1.4 States that any one of a pair of
characteristics may combine with either of another pair.
So, two characteristics must be on different chromosomes
Since any combination of chromosomes is possible in metaphase I, any one pair of characteristics may combine with either of another pair
Mitosis V. Meiosis Takes place within
somatic (body) cells Results in 2 daughter
cells Mother cell can be
haploid of diploid Is preceded by a S-phase No homologous pairing
of chromosomes Genotype of daughter
cells are identical to mother cells
•Takes place within gametes (sex cells)•Results in 4 haploid gametes•Mother cell is diploid•Only meiosis I preceded by a S phase•During prophase I, homologous chromosomes pair up•Meiotic products differ in their genotype from the mother cell
WORKS CITEDWorks Cited
"Chromosomes Crossing Over." Sciencelearn. University of Waikato, 8 June 2011. Web. 14 Feb. 2012. <http://www.sciencelearn.org.nz/Contexts/Uniquely-Me/Sci-Media/Images/Chromosomes-crossing-over>.
Farabee, M.J. "CELL DIVISION: Meiosis..." Estrella Mountain Community College. 18 May 2010. Web. 10 Feb. 2012. <http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookmeiosis.html>. Griffiths, Anthony J. F. An Introduction to Genetic Analysis. New York: W.H. Freeman, 2000. Print.
Hill, McGraw. "Stages of Meiosis." Highered.mcgraw-hill.com. McGraw Hill. Web. 10 Feb. 2012. <http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio19.swf::Stages%20of %20Meiosis>.
"IB Biology Notes - Meiosis." IB Guides - Free International Baccalaureate Study Guides, Notes, Videos and Powerpoints. Web. 10 Feb. 2012. <http://www.ibguides.com/biology/notes/meiosis>.
Khara, Kanika. "Difference Between Mitosis and Meiosis." Buzzle Web Portal: Intelligent Life on the Web.
Buzzle. Web. 14 Feb. 2012. http://www.buzzle.com/articles/difference-between-mitosis-and-meiosis.html. Kyrk, John. "Meiosis = Double Cell Division." Communicating at an Unknown Rate. 2012. Web. 14 Feb. 2012. <http://www.johnkyrk.com/meiosis.html>.
Peeters, Weem Minka., Christopher Talbot, and Anthony Mayrhofer. Biology. Melton: Ibid, 2007. Print. "Phases of Meiosis | Biology." Khan Academy. Web. 10 Feb. 2012. <http://www.khanacademy.org/video/phases-of-
meiosis?topic=biology>.