Meiosis

1
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

2

• 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.

3

• Control of the Cell Cycle
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__control_of_the_ce
  ll_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.h
  tml
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__mitosis_and_cytok
  inesis.htmlhttp//www.sumanasinc.com/webcontent/
  animations/content/mitosis.html
• Meiosis
• http//www.youtube.com/watch?vD1_-mQS_FZ0 http//
  highered.mcgraw-hill.com/sites/0072943696/student_
  view0/chapter19/animation__how_meiosis_works.html 
  
• http//highered.mcgraw-hill.com/sites/0072437316/s
  tudent_view0/chapter12/animations.html   
• Mitosis vs Meiosishttp//www.johnkyrk.com/meiosis
  .htmlhttp//www.pbs.org/wgbh/nova/baby/divide.ht
  ml http//www.pbs.org/wgbh/nova/baby/divi_flash
  .html
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__comparison_of_mei
  osis_and_mitosis__quiz_1_.html
•  

4
Meiosis

• like mitosis, meiosis follows Interphase and
• ends with cytokenisis

5

• 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

6
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)

7

• 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.

8
Metaphase I

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

9
Anaphase I

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

10
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

11
Meiosis II

12
Prophase II

• Spindle fibers form

13
Metaphase II

• chromosomes line up at the equator

14
Anaphase II

• sister chromatids separate at the centromere and
  move to opposite poles
• ttp//highered.mcgraw-hill.com/sites/0072943696/st
  udent_view0/chapter19/animation__how_meiosis_works
  .html

15
Telophase II

• 4 new nuclei appear one around each set of
  chromosomes
• followed by
• cytokenesis

16

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

17

• Review
• http//www.biology.arizona.edu/cell_bio/tutorials/
  meiosis/problems.html

18
Meiosis - Males
19
Meiosis in Females
20

• 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.