1. Bellringer
In humans, pointed eyebrows (B) are dominant over smooth eyebrows (b). Mary’s father has pointed eyebrows, but she and her mother have smooth.
What is the genotype of her father?
What are the chances that her future sibling will have smooth eyebrows as well?

2. Which of these would be a normal gamete?
GgRr
GRr Gr
GgR
None of these are normal gametes.

3. Meiosis and Sexual Reproduction
Chapter 10
Meiosis and Sexual Reproduction

4. Why Mitosis?
Mitosis maintains the same chromosome number in the daughter cells as were found in the original cell.

5. Why Meiosis?
Meiosis (or reduction division) reduces the chromosome number from 2N to N during the production of gametes.

6. Asexual Reproduction Only one parent Advantages:
Fast
Many offspring
All identical—good when well adapted to the environment
No need to find a mate
Disadvantage: no variations

7. Figure 13.1 The asexual reproduction of a hydra

8. Sexual Reproduction Usually involves two parents
Involves two events: meiosis and fertilization
Advantage: recombination of the inherited traits of two parents; therefore, offspring may be able to survive environmental changes or other stress

9. Figure Two families

10. Vocabulary Diploid (2N) Haploid (1N) Autosomes Sex chromosomes
Homologous chromosomes

12. Figure 13.4 The human life cycle

13. Figure 13.5 Three sexual life cycles differing in the timing of meiosis and fertilization (syngamy)

14. Figure 13.6 Overview of meiosis: how meiosis reduces chromosome number

15. Figure 13.7 The stages of meiotic cell division: Meiosis I

16. Figure 13.10 The results of crossing over during meiosis

17. Figure The results of alternative arrangements of two homologous chromosome pairs on the metaphase plate in meiosis I

18. Figure 13.7 The stages of meiotic cell division: Meiosis II

19. Meiosis Square Dance

20. Three Sources of Variation in Sexual Reproduction
Crossing-over
Independent assortment (223 possible combinations  8 million possibilties!)
Random fertilization

21. Compare Mitosis and Meiosis
DNA replication
Number of divisions
Type of cell you start with
Where it occurs
When it occurs
Role
Product
Events

22. Figure 13.8 A comparison of mitosis and meiosis

23. Spermatogenesis

24. Oogenesis
Unequal cytoplasmic division – why?

25. Genetic Abnormalities related to meiosis: sex chromosomes
Turner Syndrome (XO)
Klinefelter Syndrome (XXY)
Poly-X syndrome (XXX)
Jacob Syndrome (XYY)
Why no YO?

26. Genetic Abnormalities related to meiosis: autosomal
Down Syndrome (trisomy 21)
Trisomy 18
Trisomy 13
Few other autosomal abnormalities are known or occur in high frequencies – WHY?
Do not survive past the first year of life

27. Remember…
These are not gene mutations – they are IMBALANCES IN NORMAL CHROMOSOME NUMBER
How are these diagnosed?

28. Figure 13.3 Preparation of a human karyotype (Layer 1)

29. Figure 13.3 Preparation of a human karyotype (Layer 2)

30. Figure 13.3 Preparation of a human karyotype (Layer 3)
Fetal material can be obtained three ways:
Amniocentesis
Chorionic villi sampling
IVF
Controversial…why?

31. Figure 13.3 Preparation of a human karyotype (Layer 4)

32. Figure 13.x2 Human female chromosomes shown by bright field G-banding

33. Figure 13.x3 Human female karyotype shown by bright field G-banding of chromosomes

34. Figure 13.x5 Human male karyotype shown by bright field G-banding of chromosomes

35. What causes chromosomal issues like these: NONDISJUNCTION?