1. Meiosis Cornell notes

2. Meiosis animation video

3. Each one of us have characteristics passed on to us from our parents
Each characteristics we have is called a trait
The DNA on the chromosomes are arranged in segments called genes
Each chromosome consist of hundreds of genes

4. Sex cells formed by meiosis
SEXUAL REPRODUCTION
Sex cells formed by meiosis
Requires 2 parents
Offspring not identical
Meiosis
A kind of cell division that results in gametes (sex cells) with half the number of chromosomes
Gametes
In order to maintain the same chromosomes # from generation to generation,
an organism produces gametes (sex cells) that have half the # of chromosomes
Haploid
Haploid means HALF, as in the number of chromosomes,
written as n

5. Homologous Chromosomes
* Human body cells have 46 chromosomes
* Human body cells have 23 homologous pairs
Meiosis and Fertilization
One haploid gamete combines with another haploid gamete.
As a result of fertilization, the cell now will contain a total of 2n chromosomes

6. The union of an egg and a sperm
Fertilization n 2n
The union of an egg and a sperm

7. Homologous chromosomes

8. Phases of Meiosis (2 cell divisions )
Interphase
Chromosomes replicate
Chromatin condenses

9. Phases of Meiosis
(2 Cell divisions – Meiosis I & Meiosis II)
MEIOSIS I
Prophase I
Pairing of homologous chromosomes, crossing over occurs, nuclear envelope breaks down, and spindles
form

10. Metaphase I
Spindle fibers attach to homologous chromosomes (pairs) and line
up in the middle of the cell.
Anaphase I
The fibers pull the homologous chromosomes apart.
Chromosomes move toward opposite sides of the cell.

11. Telophase I
During Telophase I and cytokinesis, the spindles break down, chromosomes
uncoil and form two new nuclei, the cell divides (2 daughter cells)
**** The Chromosome number is reduced to half during Meiosis I forming haploid (n) daughter cells

12. MEIOSIS II
Prophase II
Chromosomes condense, spindle fibers form in each new cell,
Spindle fibers attach to chromosomes
Metaphase II
Chromosomes line up in the middle of the cell

13. Anaphase II
Sister chromatids separate and move towards opposite sides of the cell
Telophase II
Cells divide, resulting in 4 haploid cells – gametes (sex cells)

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

15. Summary
3 to 4 sentences of meiosis notes

16. Mitosis, Meiosis, or Neither
Number 1 - 6

17. What process is this?

18. How this sperm cell was created

19. DNA replication happens before this process.

20. When the sperm actually meets the egg.

21. I’m a single celled paramecium. Time to reproduce!

22. DNA replication happens before this process.

23. ANSWERS!
Number 1 - 6

24. What process is this?
Mitosis

25. How this sperm cell was created
Meiosis

26. DNA replication happens before this process.
Mitosis

27. When the sperm actually meets the egg.
Neither!
(Fertilization)

28. I’m a single celled paramecium. Time to reproduce!
Mitosis

29. DNA replication happens before this process.
Meiosis