1. Do Now 3/11 1) Why do cells go through the process of Mitosis?
2) Why do we look similar to our siblings, but not identical (what could be a logical explanation of this, even if you don’t know the scientific answer)?
3) Please take a sheet of paper out, tear it in half and give one half to your neighbor.

2. Quiz Time!
1) Spindle fibers start to disappear, nuclear membrane forms, and cytoplasm begins to divide.
2) Each chromatid pair splits at the centromere and separates to opposite ends of the cell.
3) Pairs of chromatids line up across the center of the cell.

3. Quiz Cont. 5) DNA is duplicated. 6) The spindle fibers form.
4) Two identical cells are formed.
5) DNA is duplicated.
6) The spindle fibers form.
7) A new nuclear membrane is forming around the chromosomes.
8) Name this phase

4. Meiosis Please grab a book and turn to page 548 in your book.
*Take a few minutes
to examine the picture
Modified by Liz LaRosa 2011

5. Terms to become familiar with
Meiosis -  cell division that results in 4 daughter cells, each with half the number of chromosomes of the parent cell
Haploid – Half the # of Chromosomes (n) , 1 of each pair of chromosomes (23)
Diploid – 2 of each type of chromosome (2n) , twice the haploid #
Homologous Chromosomes – one of two paired chromosomes, one from each parent

6. Terms Cont.
Synapsis - the pairing of two homologous chromosomes that occurs during meiosis.
Crossing Over - homologous chromosomes pair up with each other and exchange different segments of their genetic material.
Somatic Cells - A somatic cell is any biological cell forming the body of an organism.
Gametes – Sex cells or reproductive cells

7. Do Now 3/13
1) Please list two things you learned yesterday concerning meiosis.

8. Meiosis - General Overview
Sexual Reproduction and Genetics
Meiosis - General Overview
Human body cells have 46 chromosomes
Each parent contributes 23 chromosomes
Takes place in sex cells (gametes)
One cell becomes 4 NON-IDENTICLE cells

9. Chromosomes and Chromosome Number
Sexual Reproduction and Genetics
Meiosis – Homologous Chromosomes
Chromosomes and Chromosome Number
Same length
Same centromere position
Carry genes that control the same inherited traits
One is from mother, one is from father = a matching set

10. Haploid and Diploid Cells
Sexual Reproduction and Genetics
Meiosis
Haploid and Diploid Cells
An organism produces gametes to maintain the same number of chromosomes from generation to generation.
Human gametes contain 23 chromosomes.
A cell with n chromosomes is called a haploid cell.
A cell that contains 2n chromosomes is called a diploid cell.

12. Videos to begin and end with

13. Meiosis 2 Division Meiosis I (separation of homologous chromosomes)
Meiosis II (separation of sister chromatids)

14. Chromosomes replicate.
Sexual Reproduction and Genetics
Meiosis
Meiosis I
Interphase
Chromosomes replicate.
Chromatin condenses.
Interphase

15. Pairing of homologous chromosomes occurs.
Sexual Reproduction and Genetics
Meiosis
Meiosis I
Prophase I
Pairing of homologous chromosomes occurs.
Each chromosome consists of two chromatids.
Prophase I
The nuclear membrane breaks down.
Spindles form.

16. Crossing over produces exchange of genetic information.
Sexual Reproduction and Genetics
Meiosis
Meiosis I
Prophase I
Crossing over produces exchange of genetic information.
Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.

17. Chromosome centromeres attach to spindle fibers.
Sexual Reproduction and Genetics
Meiosis
Meiosis I
Metaphase I
Chromosome centromeres attach to spindle fibers.
Metaphase I
Homologous chromosomes line up at the equator.

18. Homologous chromosomes separate and move
Sexual Reproduction and Genetics
Meiosis
Meiosis I
Anaphase I
Homologous chromosomes separate and move
to opposite poles of the cell.
Anaphase I

19. The spindles break down.
Sexual Reproduction and Genetics
Meiosis
Meiosis I
Telophase I
The spindles break down.
Telophase I
Chromosomes uncoil and form two nuclei.
The cell divides.

20. A second set of phases begins
Sexual Reproduction and Genetics
Meiosis
Meiosis II
Prophase II
A second set of phases begins
as the spindle fibers forms and the
chromosomes condense.
Prophase II

21. A haploid number of chromosomes
Sexual Reproduction and Genetics
Meiosis
Meiosis II
Metaphase II
A haploid number of chromosomes
line up at the equator.
Metaphase II

22. The sister chromatids are
Sexual Reproduction and Genetics
Meiosis
Meiosis II
Anaphase II
The sister chromatids are
pulled apart at the centromere by spindle
fibers and move toward the opposite poles
of the cell.
Anaphase II

23. The chromosomes reach the poles, and
Sexual Reproduction and Genetics
Meiosis
Meiosis II
Telophase II
The chromosomes reach the poles, and
the nuclear membrane and nuclei reform.
Telophase II

24. Sexual Reproduction and Genetics
Meiosis
Meiosis II
Cytokinesis results in four haploid cells, each with n number of chromosomes.
Cytokinesis

25. The Importance of Meiosis
Sexual Reproduction and Genetics
Meiosis
The Importance of Meiosis
Meiosis consists of two sets of divisions
Produces four haploid daughter cells that are not identical
Results in genetic variation

26. Meiosis Provides Variation
Sexual Reproduction and Genetics
Meiosis
Meiosis Provides Variation
Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result.
Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine.

27. Mitosis vs Meiosis

28. Do Now 3/14 Match the description to the phase of meiosis.
1. Sister Chromatids are pulled apart. _____
A. Prophase I
2. Homologous chromosomes line up in the middle of the cell._____
B. Metaphase I
3. 2 daughter cells are formed ____
C. Telophase I
4. Nuclear membrane disappears__
D. Anaphase II
5. Nuclear membrane reforms around 4 cells ____
E. Anaphase I
6. Homologous chromosomes are pulled apart ____
F. Telophase II

29. Do Now 3/17
1) List 3 main differences between mitosis and meiosis (don’t just talk about the stages, give examples!)
2) List 3 main similarities between mitosis and meiosis (don’t just talk about the stages, give examples!)

30. Do Now 3/18
1) Did you possess more dominant or recessive traits based on the ws?
Which trait surprised you the most and why?

31. Directions What did you learn from the data?
Observe the data on the white boards. When finished with the quiz please create a bar graph that represents the data, dominant and recessive traits. Remember, you must include both dominant and recessive traits.
Helpful Hint – Y axis contains # of students while the X axis contains your traits.
What did you learn from the data?