1. MEIOSIS NOTES (11.4)

2. (Meiosis Notes 11.4) Reproduction
Asexual- all of the parent DNA goes to offspring (miTosis-mainTains)
Sexual -used to create sex cells(mEiosis-rEduce)

3. BODY CELLS SEX CELLS Chromosomes are: 1) autosomes 2) sex chromosomes
2 TYPES OF CELLS
BODY CELLS
SEX CELLS
Chromosomes are:
1) autosomes
2) sex chromosomes

4. -Also called somatic cells -Made by mitosis
Body Cells
-All cells other than sex cells
-Also called somatic cells
-Made by mitosis
This scanning electron micrograph (courtesy of Dr. Marion J. Barnhart) shows the characteristic
biconcave shape of red blood cells.

5. -Contain 2 copies of each chromosome -homologous chromosomes
Body Cells
-Contain 2 copies of each chromosome
-homologous chromosomes
-have diploid #, 2n
EX. Humans =46

6. -Eggs and sperm -Made by meiosis -Have haploid #, n -EX. Humans =23
Sex Cells
-Gametes
-Eggs and sperm
-Made by meiosis
-Have haploid #, n
-EX. Humans =23

7. How do we get 46 Chromosomes?
Egg (haploid #) + Sperm(haploid #)
ZYGOTE (diploid #)
Ex. Humans
=46

8. -starts with 1 diploid cell and ends up with 4 haploid cells
Meiosis  sex cells
mEiosis = rEduction division
-starts with 1 diploid cell and ends up with 4 haploid cells
**Meiosis I and Meiosis II

10. Meiosis I

11. ADVANTAGE: genetic variation
CROSSING OVER
Occurs during Prophase I of meiosis
*synapsis
Tetrads form and DNA is exchanged XX
ADVANTAGE: genetic variation

12.                                                               
Adapted from: Morgan T.H., Sturtevant A.H., Muller H.J., and Bridges C.B., "The Mechansim of Mendelian Heredity", 1915.
Crossing Over

13. Independent Assortment –Anaphase I

14. MEIOSIS II
Prophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
Metaphase II
The chromosomes line up in a similar way to the metaphase stage of mitosis.
Anaphase II
The sister chromatids separate and move toward opposite ends of the cell.
Telophase II
Meiosis II results in four haploid (N) daughter cells.

15. Meiosis Diagram

16. Egg Formation (unequal cytokinesis)

17. Autosomes vs. sex chromosomes

18. Comparing Mitosis and Meiosis
HOW MANY CELLS ARE MADE?
Mitosis 2
Meiosis 4

19. Comparing Mitosis and Meiosis
ARE RESULTING CELLS GENETICALLY THE SAME OR DIFFERENT?
Mitosis-
Genetically the same
Meiosis -
Genetically different

20. Comparing Mitosis and Meiosis
WHAT TYPES OF CELLS RESULT IN THE PROCESS? (BODY CELLS OR GAMETES)
Mitosis = Body cells
Meiosis = Gametes

21. Comparing Mitosis and Meiosis
WHAT ARE THE ADVANTAGES OF EACH PROCESS?
Mitosis-
Growth and repair
Meiosis-
Formation of sex cells and genetic variation