1. 30 Seconds 10 Time’s Up! 3 Minutes 1 Minute 4 Minutes 1 2 5 2 Minutes
Bellringer Mon, 12/7
What is mitosis?
What are the phases of mitosis again?
How many cells do we get after mitosis?
Quickly draw a chromosome!
Look up and tell me what is meiosis!
Use your books! 5 MINS today!
REMINDERS: HW #14 due Fri, Progress Reports
Grades this Wed,LAB FEE anytime!!!
30 Seconds 10
Time’s Up!
3 Minutes
1 Minute
4 Minutes 1 2 5
2 Minutes 8 9 7 6 4 3

2. Meiosis

3. Reminders, Review and Something New
Chromosomes = condensed chromatin (DNA)
Made up of 2 sister chromatids held together in by the centromere
Genes- sections of a chromosome responsible for one trait (eye color, height, etc)

4. Again, how many chromosomes do we have?
Meiosis
Again, how many chromosomes do we have?
23 (Maternal) + 23 (Paternal)= Total 46
1/16/2019
G. Podgorski, Biology 1010 4

7. What is MEIOSIS?
Cell division that results in 4 daughter cells with half as many chromosomes as the parent cells!

8. Meiosis Parent cell – chromosome pair Chromosomes copied
1st division - pairs split
2nd division – produces 4 gamete cells with ½ the original no. of chromosomes

9. What cells go through meiosis?
• only gametes or sex cells…. And we get…
males-sperm and females-eggs

10. Why 1/2 the chromosomes in gametes?
Why do we need meiosis?
To reduce the number of chromosomes in 1/2 in gametes (sex cells)!
Why 1/2 the chromosomes in gametes?
the male and female gametes need to provide ½ the chromosomes each – so the offspring has one complete set (1/2 from mom and 1/2 from dad)!

11. Meiosis – PMAT I and II Parent cell Meiosis I First division
Meiosis II
Second division
4 daughter cells

12. Metaphase I: homologous chromosomes align in the middle of the cell!
Meiosis
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Meiosis I
Prophase I: homologous pairs (and copies) synapse (pair up). Crossing over occurs!
Metaphase I: homologous chromosomes align in the middle of the cell!
G. Podgorski, Biology 1010

13. What are homologous chromosomes?
paired chromosomes with genes for the same trait aligned

14. Anaphase I: homologous chromosomes move to opposite ends
Telophase I: 2 nuclei form, original cell finishes to divide

15. Meiosis II No INTERPHASE or DNA copied between I and II
Prophase II: chromosomes condense again and start to move toward the center
Metaphase II chromosomes line up in the center of cells

16. Anaphase II: sister chromatids separate to opposite poles
Telophase II: two nuclei form for each of the cells
Cytokinesis happens like in mitosis! 4 daughter cells with half the amount of chromosomes formed!

17. Results after meiosis…
4 Sex cells (gametes) that are haploid (n) -
half as many chromosomes as parent cell (2n)

18. n = number of chromosomes from each parent
Meiosis
1/16/2019 n
n = number of chromosomes from each parent
Gametes (sex cells)- haploid 2n
Body cells diploid
G. Podgorski, Biology 1010

19. Diploid vs. Haploid Organism Gamete (n) Body Cell (2n) Humans 23 46
Mosquito 3 6
Toad 11 22
Potato 24 48
Dog 39 78

20. Stages of Meiosis
Meiosis I and Meiosis II

21. Meiosis
1/16/2019
G. Podgorski, Biology 1010

22. What next? Fertilization
Meiosis
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What next? Fertilization
Egg (n) + Sperm (n) = Zygote (2n)
G. Podgorski, Biology 1010

23. Zygote>Embryo>Fetus
A fertilized egg with diploid set of chromosomes.
After fertilization, the
zygote divides by
mitosis and becomes an
embryo.
Later, the embryo becomes a fetus

24. Mitosis vs. Meiosis

25. 2 Key Differences Between Mitosis and Meiosis
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2 Key Differences Between Mitosis and Meiosis
1. Look at the Way Chromosomes Pair and Align
Meiosis
Mitosis
G. Podgorski, Biology 1010

26. Chromosomes exchange genetic material between homologous pairs!
Meiosis
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2. Crossing-Over
Chromosomes exchange genetic material between homologous pairs!
G. Podgorski, Biology 1010