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Period 6 only:

Period 6 only:. * 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. ?.

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Period 6 only:

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  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: 2N DNA replication 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

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

  13. 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

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

  15. Calculate number of possible combinations in gametes: 2x2= 22= 4 2x2x2= 8 23= 2x2x2x2= 24= 16 ? ? (use calculator) 2x2….x2= 223=

  16. 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.

  17. 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.

  18. Cross- and Self-Pollination

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

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

  21. 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.

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

  23. 2N Testes Mitosis 2N 2N 1N Zygote Meiosis Fertilization Gametes 2N Ovaries 1N

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

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

  26. 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’)

  27. Quiz

  28. 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.

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