1. Period 6 only:

2. * Bats have 72 chromosomes in all of their body cells.
* The first cell of the organism is made by joining egg and sperm.
How many chromosomes in a bat egg or a sperm cell? Explain.
Can cell division by mitosis (duplication of cells) produce egg or sperm? Explain.

3. ? ?
Gametes
HUMANS! 46
Zygote

4. 23 23
Gametes
HUMANS! 46
Zygote

5. ? ?
Gametes
BATS! 72
Zygote

6. 36 36
Gametes
BATS! 72
Zygote

7. Mitosis: 1 Diploid to 2 Diploids:
DNA replication 2N 4N 2N 2N
Tetraploid
Meiosis: 1 Diploid to 4 Haploids:
DNA replication 1N 1N 4N 2N 1N 1N

8. Draw the following cell:
1) How many chromosomes?
2) How many types of chromosomes (N=?)?
3) Is this a diploid or a haploid cell? Explain.

9. Purpose: Make more identical diploid cells. Mitosis: Mitosis animation
Meiosis:
a. Reduce chromosome number by half
b. Create genetic diversity
Meiosis Animation animation

10. Period 1,2: Drawing – continued
Periods 4, 5, 6: Drawing - mitosis, meiosis
(period 6 – skip the yarn?)

11. Yarn Kit: Meiosis (finally..)
Using the four colors Show the split-split process.
What do you get?
Drawing of mitosis and meiosis

13. JOURNAL
Comparing Mitosis and Meiosis
Fill in the handout, comparing mitosis and meiosis + pictures at the bottom.

14. GENERATING VARIATION
A group-class observation
1. Make 4 egg/sperm cells from the yarn pieces (Use your drawing for reminder), N=2.
2. Draw each ‘egg’ on one quarter of a page, colored. Add to poster.
3. Eliminate repeats. How many combinations are possible?
4. Repeat procedure with N=3

15. GENERATING VARIATION: Counting combinations of chromosomes in gametes:
When N=2 There are 4 possible combinations of gametes
2N=6
When N=3 There are 8 possible combinations of gametes

16. Calculate number of possible combinations in gametes:
Haploid no., N = ?
Calculation
No. of com-binations
N=2
N=3
N=4
N=23 (human!)
2x2=
22= 4
2x2x2= 8
23=
2x2x2x2=
24= 16 ?
2x2….x2= ?
(use calculator)
223=

17. In humans, one male can make:
…. 2x2x2x2x….2=223=________
8,388,608
types of sperm.
In conclusion: Variation amongst eggs/sperm of the same individual is generated by the random segregation of homologous chromosomes in meiosis.

18. Many flowers can self-pollinate, meaning that both parents are identical.
Will their seeds grow into identical plants? Explain.
Why are we different from our siblings?
What % of our genes did we inherit from each grandparent? Explain.

19. Cross- and Self-Pollination

20. And this is not the end of it!
CROSSING OVER…
The exchange of segments between homologous chromosomes in the beginning of meiosis1.

21. Crossing over: Meiosis with crossing over Meiosis (Lewport)
Tokyo_Med Animations

22. Sources for genetic variation– a summary:
Random segregation during meiosis.
Crossing over
variation within each parent.
random selection of eggs of sperm during fertilization.
C. Different parents.

23. The Sexual Reproductive Cycle:
When is genetic variation generated?

24. 2N
Testes
Mitosis 2N 2N 1N
Zygote
Meiosis
Fertilization
Gametes 2N
Ovaries 1N

25. When is variation produced?
Mitosis 2N 2N 1N *
Meiosis
Fertilization * 2N 1N

27. Men have XY, Women have XX.
Accordingly, which of the two parents determines the gender of the child? Explain.
46xx
46xy
22+x
22+x
22+x
22+y

28. Normal Male: 46 XY
Normal Female: 46 XX
Kleinfelter Male: 47 XXY
Turner Female: 45 X
Accordingly, what determines sex – number of X’s or presence of the Y? Explain.
What question(s) do you have in regards to human chromosomes? (no ‘none’)

31. Quiz

32. If N=2:
2N:
Draw the chromosomes in a diploid cell of an organism where N=3.
How many combinations of haploid (eggs or sperm) cells are possible if N=2, N=3? Draw the possible combinations.