Meiosis

1
Meiosis
By Aaron DeVries and Sam
Desando
2
General Information

• Creates sex cells (gamete)
• Two cell divisions
• Meiosis I and Meiosis II
• In females only one daughter
  cell can actually function

3

• http//www.biology.arizona.edu/CELL_BIO/tutorials/
  meiosis/page3.html

4
Prophase I

• Nuclear envelope fragments
• Nucleous disappears
• Spindle fibers form
• Sister chromatids undergo synapsis to form
  tetrads
• Crossing over (genetic recombination)

5
Prometaphase I

• Nuclear membrane disappears
• One centromere forms per
  chromosome
• Chromosomes attach to spindle fibers and begin to
  move

6
Metaphase I

• Tetrads align at metaphase
  plate
• Random order gives
  you all possible combinations of chromosomes
• Fully formed spindle

7
Anaphase I

• Homologues of each
  tetrad separate and
  move to opposite poles
• Each chromosomes still have two chromotids

8
Telephase I

• Spindle disappears
• Daughter cells are
  diploids (46 chromosomes)

9
Cytokinesis/ Interkinesis

• Similar to interphase
  of mitosis where two
  daughter cells form

10
Meiosis II

• Prophase II
• Metaphase II
• Anaphase II
• Telophase II
• Daughter cells form
• Result in four haploid
• daughter cells
• Sex cells (23 chromosomes in each)

11
Spermatogenesis

• In males, all four sperm cells are functional
• Meiosis only occurs after puberty

12
Oogenesis

• Occurs in females, only one of the two eggs is
  functional
• Secondary oocyte functional egg (receives most
  of cytoplasm)
• Polar body non functional
• Meiosis I, only occurs during fetal development
• Meiosis II only occurs after fertilization

13
Disorders

• http//learn.genetics.utah.edu/units/disorders/kar
  yotype/karyotypeinfo.cfm

• Down Syndrome - trisomy Chromosome 21
• Turner syndrome monosomy of X chromosomes
• Klinefelter syndrome trisomy of X and Y, two
  Xs and one Y
• All result from trisomy or monosomy
• Monosomy- missing copy of chromosomes
• Trisomy- three copies of one chromosomes

14
Sources

• http//www.accessexcellence.org/RC/VL/GG/meiosis.h
  tml
• http//www.biology.arizona.edu/CELL_BIO/tutorials/
  meiosis/page3.html
• http//www.funnypictureslady.com/funnybabies/pages
  /p0037.php
• http//learn.genetics.utah.edu/units/disorders/kar
  yotype/karyotypeinfo.cfm
• http//highered.mcgraw-hill.com/classware/ala.do?i
  sbn0072464631alaidstructure_661712showSelfStud
  yTreetrue
• Biology book, Chapter 10