1. Mysterious Meiosis

3. I. Very Important Vibrant Vocabulary
Heredity: Transmission of traits from one generation to the next
Variation: Offspring differ from parents and siblings
Genetics: Scientific study of heredity and hereditary variation
Locus: A gene’s specific location along the length of a chromosome

5. III. Very Important Vibrant Vocabulary
Genes program cells to make proteins, proteins produce traits

6. III. Very Important Vibrant Vocabulary
Karyotype: Organization of a cell’s chromosomes by number, size, and type
Diploid: A cell with a full set of chromosomes (23 pair = 46 chromosomes)
Homologous Pairs: A pair of chromosomes (chromatids) that have the same genes, but different forms of the genes (1 from mom, 1 from dad)

8. III. Very Important Vibrant Vocabulary
Sex Chromosomes: A special pair of chromosomes that make us girl or boy
XX-Female XY-Male (non-homologous)
Autosomes: The 22 other pairs of chromosomes
Tetrad: Homologous chromosomes that are copied and stuck at the centromere.
(Four copies of the chromosome, Two from each parent)

10. III. Very Important Vibrant Vocabulary
Haploid (gametes): Cells with half the chromosomes, No homologous pairs
22 autosomes + 1 sex chromosome = 23 chromosomes
Zygote: Haploid sperm and haploid egg = Diploid zygote

14. IV. Meiosis...The Details
Diploid 46 to Haploid 23

15. 1. Interphase I
**DNA Replication occurs

16. IV. Meiosis...The Details 2. Prophase I Homologous pairs partner up
Synapsis...Attaches homologous chromosomes tightly together into a tetrad
Crossing over occurs now
Spindle fibers form, nuclear membrane disappears

18. IV. Meiosis...The Details 3. Metaphase I
Chromosomes line up on metaphase plate in homologous pairs

20. IV. Meiosis...The Details 4. Anaphase I
Sister chromatids remain attached at centromere
Move as a unit to the poles

22. IV. Meiosis...The Details
5. Telophase I and Cytokinesis
Cells split

24. IV. Meiosis...The Details
6. Prophase II
Spindle forms

25. IV. Meiosis...The Details
7. Metaphase II
Line up in the middle again

27. IV. Meiosis...The Details 8. Anaphase II
Centromeres break and sister chromatids (chromosomes) move to the poles

29. IV. Meiosis...The Details 9. Telophase II and Cytokinesis:
Chromosomes to Chromatin
Four daughter cells are formed
Ta da!! Sex Cells!!

31. V. Sources of Variation in Meiosis
A. INDEPENDENT ASSORTMENT
When chromosomes line up during Metaphase I, they do so independently of each other. This results in different combinations of chromosomes in gametes because every time they line up they do it differently.

33. V. Sources of Variation in Meiosis
B. CROSSING OVER
During Prophase I, homologous chromosomes pair tightly and pieces of one chromosome can cross over to the homologous chromosome. This results in chromosomes that have a combination of maternal and paternal genes.

35. V. Sources of Variation in Meiosis
C. RANDOM FERTILIZATION
The egg that is fertilized is one of 8 million chromosome combos. The sperm that reaches the egg is also one of 8 million combos. This results in over 64 trillion combos of sperm and egg from one set of parents (this is without
crossovers).
Be sure to look over page 242, Figure 13.8!!! Very possible essay!!!!

37. VI. Gametogenesis in Humans (pg. 985-987)
A. Oogenesis
Production of ova, mature eggs
Occurs in the ovary.
Oogonia: Stem cells that make eggs

38. A. Oogenesis
These stem cells multiply and then begin meiosis. They stop meiosis at Prophase I. The cells at this stage are called Primary Oocytes. The cells remain here as follicles until puberty.

39. A. Oogenesis
Follicle-stimulating Hormone stimulates a follicle to grow and complete Meiosis I and to start Meiosis II.
Meiosis II stops....now the cell is called a Secondary Oocyte.
Ovulation occurs, the cell then finishes Meiosis II when it is penetrated by a sperm.

42. B. Spermatogenesis Production of mature sperm
Occurs in the seminiferous tubules of the testes.
Spermatogonia: Stem cells that make sperm
million sperm per ejaculation. Men can ejaculate daily with no loss of fertility capactity.

45. C. The difference between Spermatogenesis and Oogenesis
In oogenesis meiotic divisions are unequal (cytokinesis).
One egg cell is created, three small polar bodies degenerate
In spermatogenesis meiotic divisions are equal.
Four sperm are created from each spermatogonia

46. C. The difference between Spermatogenesis and Oogenesis
At birth, the ovary contains all of the primary oocytes it will ever have. Spermatogonia go through meiosis all through a man’s life.
Oogenesis has long “resting” periods. Spermatogenesis is uninterrupted.