1. Meiosis

2. The Diploid Cell Cell with ___ sets of chromosomes
Contains chromosomes for each _________ pair
__________ = Body Cells: Diploid
All human cells except ___________ are diploid
Where does the diploid number come from?
____, where n is the number of chromosomes an individual has
What is n for humans? ______ 2n? ______

3. The Haploid Cell Cell containing ___ of each kind of chromosome
Examples: ___________________
___ set of chromosomes
_____ the number of chromosomes of diploid
___
Sperm + Egg = Zygote

4. Haploid = one of each kind Diploid = two of each kind
2n = diploid n = haploid + or

5. Mitosis vs. Meiosis
Mitosis: t = two: Diploid n=46
Meiosis: o = one: Haploid
n = 23

6. Meiosis __________ are produced in specialized body cells
Sperm and Egg Cells
__ divisions: _______________________
Meiosis occurs in ____ cells, not _____ cells
__ daughter cells
Each cell has ____ the chromosomes of the parent

7. Meiosis I Interphase occurs: the cell grows and DNA replicates
Meiosis I begins
Original cell produces two new cells
Like Mitosis

8. Prophase I DNA Coils tightly into chromosomes Spindle fibers appear
Each chromosome lines up next to the homologue
Synapis occurs: pairing of homologous chromosomes
Tetrad: Each pair of homologous chromosomes

9. Crossing Over
Crossing Over: why we do not look exactly like our parents.
Portions of the ___________ breaks off and attaches to _______________ on the _____________ chromosome
Permits __________________________ between maternal and paternal chromosomes
Occurs during _____________

11. Genetic Recombination
Crossing over produces a new mixture of genetic material

12. Causes of Variation Chromosomes are assorted randomly
Crossing over may occur
Cells do not have identical genetic info as each other or the parent
+ ____________________________
- _____________________________

13. Metaphase I Tetrads line up randomly along the mid-line
Spindle fibers attach to centromeres

14. Anaphase I Homologous chromosomes move to the opposite poles
Random separation or Independent Assortment results in separation of maternal and paternal chromosomes.

15. Telophase I Chromosomes reach opposite ends of cell Cytokinesis begins
Cell is now haploid

16. Meiosis II Occurs in each cell formed in Meiosis I
Interphase does not occur again

17. Prophase II
Spindle fibers form and move the chromosomes to the mid-line of the dividing cell

18. Metaphase II
Chromosomes move to the mid- line of the dividing cell facing opposite poles of the dividing cell

19. Anaphase II
Chromatids separate and move to opposite poles of the cell

20. Telophase II
Nuclear membrane forms around the chromosomes in each of 4 new cells

21. Cytokinesis II
__________ divides
____________________ closes off

22. End Result:
____ new cells that contain _____ of the original cells number of chromosomes
Creates _________ = _________

23. What exactly is a gamete?
Formed by ________
___________________ cells
In humans, meiosis occurs in the testes and ovaries

24. Meiosis Animation
Meiosis Animation

25. Why do we need haploid gametes?
EGG 23
Female gamete
Male gamete 23
SPERM

26. Fertilization restores the diploid number
meiosis 1n
fertilization 2n 2n
Mitosis and cell growth 2n

28. Mitosis vs. Meiosis
Mitosis vs. Meiosis Animation
Notes:

29. Nondisjunction
Failure of ___________________ to ___________ properly during meiosis.
__________________ of a homologous pair move to the ____________ of the cell.
1 gamete has ___________________ Or
1 gamete is ______________________

30. Nondisjunction Animation
Notes:

31. Chromosome Pop Quiz! What is a chromosome? Where do we find them?
What do they look like?
How many pairs of chromosomes do humans have?
What determines if someone is male or female?

32. Trisomy: Extra Chromosomes
Trisomy 13: Patau’s Syndrome
Trisomy 21: Down’s Syndrome
XXX: Trisomy X
XYY: Jacob’s Syndrome
XXY: Klinefelter’s Syndrome

33. Monosomy: Missing Chromosomes
Most do not survive.
Turner XO : develop as girls, but infertile
OY: lethal