1. MEIOSIS … making gametes….

2. Quick Review Gamete = sex cells (egg and sperm)
Each has 1 set of 23 chromosomes
When they come together, the resulting cell has 46 chromosomes
Somatic cell = body cells (everything except egg and sperm) 23 23

3. Cells with 1 set of chromosomes (gametes) are said to be HAPLOID (n)
Each of your body (somatic) cells has 2 sets of chromosomes – one from mom, one from dad.
Any cell that has 2 complete sets of chromosomes is said to be DIPLOID (2n)
Cells with 1 set of chromosomes (gametes) are said to be HAPLOID (n)
When 2 cells come together in fertilization to make a zygote, each can only have 1 set of chromosomes. That way, the zygote will have 46 chromosomes. ( = 46)
(Instead of = 92!)

4. What type of cells produce egg/sperm?
Ovarian and testicular cells!

5. Meiosis is… Making the cells that make babies! (egg and sperm)
The process of nuclear division that reduces the number of chromosomes by half (reduction division)
Start with somatic cell
End with gamete

6. More practice…
In streptomycin fungus n = 11. What is the diploid number for this species?
If 2n = 108 for black spruce trees then what is the haploid number?
2n = 14 for this species. Fill in the chromosome numbers for each cell. A C B
What is process A, B, and C?

7. Homologous Chromosomes (pairs)
In each body (somatic) cell you have 23 homologous chromosome pairs
Similarities: length, centromere location, and code for same traits (have same genes)
Differences: one chromosome from mom and one from dad

8. Homologous Chromosomes have the same banding pattern

9. Diploid Testicular cell
Diploid ovarian cell
Diploid Testicular cell
How you got here:
2n n
egg (n) sperm (n)
fertilization
zygote
MEIOSIS
MEIOSIS
MITOSIS
You

10. Products of MITOSIS: Products of MEIOSIS: 4 unique haploid (n) cells
2 identical diploid
(2n) cells
Products of MEIOSIS:
4 unique haploid (n) cells
2n n n
2n n n n n

11. Why Meiosis is important:
It creates Genetic Recombination (variety):
Resulting from crossing over AND independent assortment
Crossing Over:
Exchange of genetic material between homologous chromosomes during prophase I of Meiosis

12. Crossing Over: Exchange of genetic material between homologous chromosomes

13. Independent Assortment: ending up with random mix of genes in each gamete

14. MEIOSIS I
1. Interphase I: Period of cell growth and preparation for division (G1, S, G2)
PROPHASE I:
Tetrads appear
Crossing Over (synapsis) occurs -
Before Interphase
After interphase

15. Metaphase I: Tetrads (2 homologous chromosomes) line up on metaphase plate and lock on to spindle fibers
 Anaphase I: Spindle fibers pull tetrad apart; one homologous chromosome goes to each side of the cell. Independent assortment occurs

16. Telophase I: nuclear membranes form around the two new nuclei
Cytokinesis I: cell splits in two. Result = 2 diploid cells.

17. MEIOSIS II

18. *Special Interphase between the two divisions:
NO replication!!! - so nothing changes with the chromosomes between telophase I and prophase II

19. Prophase II: When chromosomes show up you will see sister chromatids.
Metaphase II: Chromosome made of Sister chromatids line up on equator
Anaphase II: Sister chromatids are pulled apart.
Telophase II: Nuclear membranes form.

20. Cytokinesis: cytoplasm divides
Total product is 4 haploid (n) gametes

22. Uneven cytokinesis in females: In oogenesis (female meiosis), get one big egg and 3 non-functional polar bodies (non-functional cells that die)

23. OOGENESIS
First division: results in one big primary oocyte and a little polar body.
Second division: One secondary oocyte and 3 polar bodies. (polar bodies die) 2n
Oogonium (what you’re born with)
At puberty, oogonia mature into primary oocytes 4n
Secondary oocyte
Polar Body
3 Polar Bodies
ovum n n n n

24. Equal divisions producing four useable sperm
Spermatogenesis
Equal divisions producing four useable sperm

25. Spermatagonium  primary spermatocyte  2 secondary spermatocytes  4 spermatids
Spermatids mature into spermatazoa. Once spermatazoa are released, we call them sperm

26. Meiosis vs. Mitosis (Make a chart)
Used for Sexual Reproduction
Produces Gametes (Egg & Sperm)
Have 23 chromosomes
2 sets of divisions
Begins with a diploid cell
Homologous chromosomes pair up
Result: 4 genetically different HAPLOID SEX cells
Used for Growth and Asexual Reproduction
Produces body cells
Have 46 chromosomes
Somatic cells
One round of division
Begins with diploid cells
No crossing over
Homologous chromosomes don’t pair up
Results in 2 genetically identical DIPLOID SOMATIC cells

27. Plants…the oddballs
Plants have a 2-part life cycle; each cycle uses a different body structure
Diploid phase: sporophyte (makes spores)
Haploid phase: gametophyte (makes gametes)
*Developed to protect the embryo as it grows

28. Flowering Plants

29. Sporophyte generation
begins with zygote

31. Karyotype = picture of all chromosomes in 1 cell
Used to determine:
If there is an abnormality in number or structure of the chromosomes
(e.g. Down’s syndrome)
2. Gender

32. Karyotypes can be obtained in several ways
In a developing fetus:
CVS (chorionic villus sampling) and amniocentesis
In children and adults:
Karyotypes can be obtained from any growing cells.
(Can a karyotype tell if there are any GENE mutations?)

33. Figure 12Ba

34. Figure 12Bb

35. Non-disjunction
Non-separation of chromosomes resulting in diploid or empty gametes
When it happens in Meiosis I:
All 4 gametes affected
When it happens in Meiosis II:
½ of gametes affected

37. DOWN SYNDROME (trisomy 21)
Figure 12.11

38. Turner Syndrome (Monosomy X) Infertility Webbed neck Short stature
Figure 12.12a
Turner Syndrome (Monosomy X)
Infertility
Webbed neck
Short stature
May fail to start puberty

39. Klinefelter Syndrome (XXY):
Figure 12.12b
Klinefelter Syndrome (XXY):
Presents as male
Infertility
Feminine Characteristics:
Enlarged breast tissue
Wide-set hips
Cognitive deficits
Treated with testosterone

40. Trisomy 18 - Edward's Syndrome
Failure to grow and gain weight at the expected rate and severe feeding difficulties, diminished muscle tone and episodes in which there is temporary cessation of spontaneous breathing
Developmental delays and intellectual disability
A prominent back portion of the head, low-set, malformed ears, an abnormally small jaw, a small mouth an upturned nose, narrow eyelid folds, widely spaced eyes, and drooping of the upper eyelids

41. TRISOMY 13 (also known as Patau syndrome) - Of all babies born with the extra copy of chromosome 13 in all the cells of their body, around 50% die in the first month, and the rest within the first year Median survival age for children with Patau syndrome is 2.5 days

42. CHROMOSOME MUTATIONS

43. Figure 12.13

44. Figure 12.13a

45. DELETION MUTATION (WILLIAMS SYNDROME-chromosome 7)
Characteristic face shape, cardiovascular problems, affinity for music

46. CRI DU CHAT Deletion of Chromosome #5
Cries are high-pitched; sound like cats
Eyes have downward slant
Partial webbing of digits
Small Jaw

47. Figure 12.13b

48. FRAGILE X - duplication mutation

49. Figure 12.13c

50. Figure 12.13d

51. Greig Cephalopolysyndactyly syndrome
Figure 12.16
Enlarged forhead and webbed digits
Greig Cephalopolysyndactyly syndrome

52. Figure 12.16b