1. To be successful today…
Pull out notes: Meiosis
BYOD Color of the day is Phones are in put away in backpacks

2. MEIOSIS
The reduction division…

3. Recall… CHARACTERISTICS OF LIVING THINGS:

4. Binary fission, budding & regeneration
ASEXUAL REPRODUCTION
Binary fission, budding & regeneration
Planaria animation:

5. ASEXUAL REPRODUCTION & MITOSIS

6. ADVANTAGES OF ASEXUAL REPRODUCTION
Can make offspring faster
Don’t need a partner

7. DISVANTAGES OF ASEXUAL REPRODUCTION
ALL ALIKE
Species CAN’T change and adapt

8. Combines genetic material genetically different
SEXUAL REPRODUCTION
Family image from:
Combines genetic material
from 2 parents
Offspring are
genetically different
from parents

9. ADVANTAGES OF SEXUAL REPRODUCTION
Variation in population
Species can adapt to
changes in their environment

10. Think-Pair-Share
Human body cells contain 46 chromosomes 1. How many chromosomes would a sperm or an egg cell contain if either one resulted from the process of mitosis?

11. Think-Pair-Share
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?

13. Think-Pair-Share
3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg cell have?

14. DIPLOID VS HAPLOID
Body cells (somatic cells) have 2 copies of each chromosome
DIPLOID (2n)

15. DIPLOID & HAPLOID Sex cells (sperm & egg) have only
one copy of each chromosome
Haploid = 1N

16. Diploid vs Haploid Video

17. MITOSIS CREATES DIPLOID BODY CELLS

18. MEIOSIS CREATES HAPLOID SEX CELLS
Makes 4 cells genetically different from parent cell & from each other
Used for sexual reproduction

19. HOMOLOGOUS CHROMOSOMES
SAME SIZE
SAME SHAPE
CARRY GENES for the SAME TRAITS
BUT NOT IDENTICAL!

20. Stages of Meiosis

21. Meiosis

22. Meiosis takes place in two series of steps
Meiosis I I, P, M, A, T +
Meiosis II P, M, A, T
Which means…no DNA replication before meiosis II
No second “I”

23. Interphase I
DNA replicates creating homologous chromosomes

24. PROPHASE I Homologous chromosomes pair up = SYNAPSIS TETRAD
This group of FOUR (4)
chromatids is called a
_________________
TETRAD
Images modified from:

25. Exchange of DNA between homologous pairs
2. CROSSING OVER
Exchange of DNA between homologous pairs
After crossing over, chromatid arms are NOT IDENTICAL anymore

26. Metaphase I
Tetrads line up in the middle

27. Anaphase I- Tetrads pull apart to opposite ends of the cell.

28. Telophase I- Cell separates into two new cells

29. No Interphase II which means chromosomes are NOT copied again.
Meiosis II
No Interphase II which means chromosomes are NOT copied again.

30. Prophase II ~ TWO cells begin meiosis II

31. Metaphase II: chromosomes line up in the middle of the cell

32. Anaphase II : chromosomes are pulled to opposite ends of the cell

33. Telophase II / Cytokinesis ~ The two cells divide to form 4 genetically different cells (gametes)

34. End Result of Meiosis Four new cells (gametes)
Half # chromosomes as parent cell - haploid (n)
Humans – 23 chromosomes

35. Meiosis Video

36. MAKING SPERM & EGGS

37. ___________________= MAKING MATURE SPERM
SPERMATOGENESIS
___________________= MAKING MATURE SPERM
Mature & grow flagella
Sperm cells take a couple of days to go through meiosis & mature

38. CYTOPLASM DIVIDES UNEVENLY in both divisions;
OOGENESIS
__________________ =
MAKING a MATURE EGG
Producing:
1 “good” egg
3 polar bodies
CYTOPLASM DIVIDES UNEVENLY in both divisions;
POLAR BODIES DEGENERATE (DIE)

39. More about the female gamete…
Females are born with their lifetime supply of eggs. The first meiotic division occurs before birth. The second division occurs at the time of ovulation somewhere between the ages of 12 and 40 years.

40. What are the major differences between Mitosis and Meiosis?

41. Mitosis Meiosis Body cells (Somatic) Sex cells (Gamete)
2 daughter cells same as parent cell (diploid – 2n)
4 daughter cells w/half chrom. (haploid – 1n)
Asexual reproduction
Sexual reproduction