1. Drill # 15: In your notebook, create a Venn Diagram comparing Meiosis vs. Mitosis by looking at the pictures

2. SWBAT Describe the steps of Meiosis
List the differences between Meiosis and Mitosis

3. Agenda Meiosis Notes - http://rallanwebpage.weebly.com/
Homework: Complete comparison chart

4. Meiosis
Division of the nucleus that reduces the number of chromosomes in new cells in half.
Goes through PMAT twice

5. Homologous Chromosomes:
Prophase I:
Prophase I: Chromosomes become visible. The nuclear membrane breaks down.
Homologous Chromosomes:
Two identical copies of the same chromosomes.
One chromosome from each parent.

6. Prophase I: Crossing-Over:
Portions of chromatids may break off and attach to a nearby chromatid
PURPOSE – Permits the exchange of genetic material between mom and dad chromosomes (i.e., a new mixture of genetic material)
Prophase I: Chromosomes become visible. The nuclear membrane breaks down.

7. Metaphase I:
Metaphase I: Pairs of homologous chromosomes move to the middle of the cell.

8. Anaphase I: Independent assortment- A random
Anaphase I: Homologous chromosomes move to opposite poles of the cell.
Independent assortment-
A random
separation of mom and dad chromosomes which results in genetic variation

9. Telophase I:
Telophase I: Chromosomes gather at the poles. Nuclear membrane reappears. The cytoplasm divides.

10. END OF MEIOSIS I:
Original cell produces 2 new cells. Each new cell contains one chromosome from each homologous pair (i.e., half the number of chromosomes as the original)

11. Prophase II:
Prophase II: A new spindle forms around the chromosomes. Nuclear membrane breaks down.

12. Metaphase II:
Metaphase II: Chromosomes line up in the middle.

13. Anaphase II:
Anaphase II: Centromeres divide and chromatids move to opposite poles.

14. Telophase II:
Telophase II: A nuclear envelope forms around each set of chromosomes. The cytoplasm divides.

15. Diploid vs Haploid
Cells having two sets of chromosomes are said to be diploid (2n)
Ex: normal human body cells 2n=46
Cells that contain only one set of chromosomes are said to be haploid (1n)
Ex: Human sperm cells and egg cells 1n=23

16. END OF MEIOSIS II:
4 new cells, each containing half of the original cell’s number of chromosomes
In animals, meiosis produces haploid reproductive cells called gametes.
ONLY REPRODUCTIVE CELLS GO THROUGH MEIOSIS!

17. 2 Types of Meiosis Spermatogenesis-production of sperm
Produces 4 sperm cells

18. Oogenesis-production of an egg cell
Only 1 egg cell is produced
3 other polar bodies get recycled

19. Wrapup
Write down 2 similarities and 2 differences between meiosis and mitosis.

20. Drill #7: Feb. 9 & 10, 2012
List 2 ways meiosis is different from mitosis.
Why is only 1 egg cell produced during oogenesis?

21. Drill #7: Feb. 9 & 10, 2012
List 2 ways meiosis is different from mitosis. PMAT twice, 4 vs 2 cells produced, cells are not identical
Why is only 1 egg cell produced during oogenesis? This cell has most of the cytoplasm and nutrients in case the egg is fertilized.

22. Objectives
SWBAT Differentiate between a gene, DNA molecule, a chromosome, and a chromatid.
SWBAT Differentiate between homologous chromosomes, autosomes, and sex chromosomes.
SWBAT Predict how changes in chromosome number or structure can affect development.

23. Agenda Complete Meiosis & Mitosis Comparison Karyotypes/Chromosomes
Genetic Vocabulary
Mendel’s Experiments
Turn in Asexual Reproduction WS

25. Homologous chromosomes
Carry genes that control the same characteristics (eye color, height, blood type)
Locus = physical location on a chromosome for that gene
Allele = different forms of the same gene

27. Types of Chromosomes Sex chromosomes- determine the sex of an organism
in humans: X or Y (are not homologous)
Female is XX
Male is XY (X is much larger with more genes)
Autosomes-all other chromosomes in an organism
Every cell (except sex cells) has 2 copies of each autosome
Homologous chromosomes-Two identical copies of the same chromosomes.
One chromosome from each parent

29. Karyotype
A photo of the chromosomes in a dividing cell that show the chromosomes arranged by size.
Chromosomes can be
sorted into pairs using
size, length, position of
centromere, and banding
patterns.