1. MEIOSIS 11-4 Making gametes…
Making gametes…

2. Interest Grabber
1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?
2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?
3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?
46 chromosomes
= 92; a developing embryo would not survive if it contained 92 chromosomes.
Sperm and egg should each have 23 chromosomes.

3. Objectives Contrast the chromosome # of body cells and gametes
Summarize the events of meiosis
Contrast meiosis and mitosis

4. + EGG SPERM  If egg and sperm had same number of
Image by Riedell
Image by Riedell
EGG +
SPERM 
If egg and sperm had same number of
chromosomes as other body cells . . .
baby would have too many chromosomes!

5. MEIOSIS is the way… to make cells with ½ the number of chromosomes
for sexual
reproduction

6. Click the image to play the video segment 11A.
Meiosis Overview
Click the image to play the video segment 11A.
Video 1

7. DIPLOID & HAPLOID HOMOLOGOUS CHROMOSOMES
Most cells have 2 copies of each chromosome = ______________
(one from mom; one from dad)
All BODY (___________) cells are diploid
DIPLOID 2n
HOMOLOGOUS CHROMOSOMES
= SOMATIC

8. HOMOLOGOUS CHROMOSOMES
SAME SIZE
SAME SHAPE
CARRY GENES for the SAME TRAITS
BUT ______________!
(Don’t have to have the SAME CHOICES)
Image modified by Riedell
NOT IDENTICAL

9. DIPLOID & HAPLOID
Some cells have only one copy of each chromosome = _____________
All sperm and egg cells
are haploid
HAPLOID 1n

10. MITOSIS REVIEW
Makes ___ cells genetically _________ to parent cell & to each other
Makes ___ cells
Makes __________
Used by organisms to: increase size of organism, repair injuries, replace worn out cells 2
identical 2n
SOMATIC (body)

11. MEIOSIS 4 1n Gametes (sperm & eggs) sexual reproduction
Makes ____ cells genetically different from parent cell & from each other
Makes _____ cells
Makes ______________
Used for ____________ 1n
Gametes (sperm & eggs)
sexual reproduction

12. PREDICT THE OUTCOMES Unicorns have 40 chromosomes
After Mitosis
Two 2n cells each with 40 chromosomes
After Meiosis
Four 1n cells each with 20
Loch Ness Monsters have 50 chromosomes
Two 2n cells each with 50
Four 1n cells each with 25

13. PREDICT THE OUTCOME
You are studying a cell with 20 chromosomes, and it goes through a process that produces haploid cells.
What is the process called?
How many chromosomes would be in the new cells?
How many cells would you now have?

14. WHAT MAKES MEIOSIS DIFFERENT ?
SYNAPSIS & CROSSING OVER (PROPHASE I)
SEGREGATION &
INDEPENDENT ASSORTMENT (ANAPHASE I)
3. Skip INTERPHASE II (NO S)
CELL DIVIDES TWICE, BUT…
ONLY COPIES DNA ONCE

15. WHAT MAKES MEIOSIS DIFFERENT ?
Homologous chromosomes pair up during ________________
= ______________
PROPHASE I
SYNAPSIS
This group of FOUR (4)
chromatids is called a
_________________
TETRAD
Images modified from:

16. WHAT MAKES MEIOSIS DIFFERENT?
1. Exchange of DNA between homologous pairs = _____________ during PROPHASE I
CROSSING OVER
Allows shuffling of genetic material

17. Click the image to play the video segment. 11E
Crossing Over
SEE CROSSING OVER ANIMATION
Click the image to play the video segment. 11E
Video 5

18. WHAT MAKES MEIOSIS DIFFERENT ?
2.Separation during ANAPHASE I
SEGREGATION &
INDEPENDENT ASSORTMENT
Separates gene choices and allows shuffling of genetic material

19. Click the image to play the video segment 11D.
Segregation of Chromosomes
Click the image to play the video segment 11D.
Video 4

20. SEGREGATION (Anaphase I)

21. SEGREGATION & CROSSING OVER together make even more combinations
See an animation

22. INDEPENDENT ASSORTMENT

23. INDEPENDENT ASSORTMENT at ANAPHASE I
Lots of different combinations are possible!
This is why you don’t look exactly like your brothers and sisters even
though you share the same parents!

25. WHAT MAKES MEIOSIS DIFFERENT ?
Crossing over Segregation Independent assortment
are ALL ways MEIOSIS results in =______________________________
So daughter cells are ______________
from parents and from each other
GENETIC RECOMBINATION
different

26. WHAT MAKES MEIOSIS DIFFERENT ?
3. Skip INTERPHASE II (No S)
CELL DIVIDES TWICE, BUT …
ONLY COPIES ITS DNA ONCE
MITOSIS: G1 S G2 P M A T C       
MEIOSIS:
( I ) G1 A T C S G2 P M        P M A T C
( II )    

27. Click the image to play the video segment 11B. & C
Animal Cell Meiosis, Part 1 & Part 2
Click the image to play the video segment 11B. & C

28. MITOSIS vs MEIOSIS INTERPHASE INTERPHASE I
SAME

29. MITOSIS vs MEIOSIS PROPHASE PROPHASE I
Homologous pairs match up

30. MITOSIS vs MEIOSIS METAPHASE METAPHASE I
Tetrads line up in middle

31. MITOSIS vs MEIOSIS ANAPHASE ANAPHASE I
APART:
Tetrad splits apart

32. MITOSIS vs MEIOSIS TELOPHASE TELOPHASE I
SAME

33. MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS I
SAME

34. MITOSIS vs MEIOSIS INTERPHASE II
SKIP
INTERPHASE II
DNA NOT COPIED

35. MITOSIS vs MEIOSIS PROPHASE PROPHASE II
SAME

36. MITOSIS vs MEIOSIS METAPHASE METAPHASE II
SAME

37. MITOSIS vs MEIOSIS ANAPHASE ANAPHASE II
Same

38. MITOSIS vs MEIOSIS TELOPHASE TELOPHASE II
SAME

39. MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS II
SAME

40. MAKING SPERM & EGGS

41. ___________________= MAKING MATURE SPERM
SPERMATOGENESIS
___________________= MAKING MATURE SPERM
Mature & grow flagella

42. Sperm provides DNA
All the starting nutrients,
organelles, molecule building blocks,
etc. have to come from the egg.

43. CYTOPLASM DIVIDES UNEVENLY
OOGENESIS
__________________ =
MAKING a MATURE EGG
Produces:
1 “good” egg 3
POLAR BODIES
CYTOPLASM DIVIDES UNEVENLY

44. Sperm donates mostly DNA
WHY MAKE ONLY ONE “GOOD” EGG?
Sperm donates mostly DNA
Most of the cell parts and nutrients needed for baby come from EGG!

45. After cell division, how many chromosomes are in the body cells of humans?42 46 23 21

46. After cell division, how many chromosomes are in the body cells of humans?42
46 Correct! 23 21

47. After cell division, how many chromosomes are in the sex cells of humans?42 46 23 21

48. After cell division, how many chromosomes are in the sex cells of humans?42 46
23 Correct 21

49. What events of meiosis allows for genetic recombination in meiosis?
Crossing over
Crossing over, independent assortment
Synapsis
tetrad

50. What events of meiosis allows for genetic recombination in meiosis?
Crossing over
Crossing over, independent assortment Correct!!
Synapsis
tetrad