1. Welcome Back!

2. Welcome Back! Put your name on the new stamp sheet.
If you have a new journal, you can start fresh for the semesters.
Set-up your journals for our next unit:
Unit 8-Genetics

3. Why do you and your siblings look different?

4. How did the difference in our DNA occur?
If we share the same parents?

6. Welcome back!
Set-up next Unit:
Unit 8-Genetics

7. Let’s review: The cell cycle (cell division)
Mitosis

8. Mitosis only creates cells to help our body grow
In these cells they have identical DNA

9. There are 2 category of cells in our body: somatic and sex cells
Somatic Cells(body cells)
Any cell that helps in the growth of an organism
Is diploid (2n)-paired chromosomes
Example: skin, muscle, blood cells
Gametes (sex cells)
Eggs and Sperm
Reproductive cells of an organism
Is haploid (n)-unpaired chromosomes

10. What is Meiosis?
Form of cell division in which the number of chromosomes is reduced by half (haploid) to produce sex cells (gametes) used in fertilization.
Results in variability of genetic information
Increases Genetic Variation!
Eggs or sperm

11. Mitosis vs. Meiosis
With your partner create a t-chart in your notebook and come up with as many differences between Mitosis and Meiosis (use the diagram to help you)
(2n)
(2n)
(2n)
(2n)
(n)
(n)
(n)
(n)

12. Mitosis Vs. Meiosis (If you don’t have this information copy it into your notebook)
Division of somatic/body cells
1 division = 2 cells
Daughter cells identical
Diploid cells (2n) =46 in humans
Chromosome # identical to parent cell
Used for growth and repair
Meiosis
Division of gametes (sex cells—eggs or sperm)
2 divisions = 4 cells
Daughter cells different (crossing over; independent assortment)
Haploid cells (n)=23
Chromosome # half of parent cell
Used for reproduction

13. How is Meiosis Different?
There are 2 divisions in meiosis
Meiosis I and meiosis II
The result is 4 daughter cells instead of 2
In meiosis II, the DNA is not replicated again (No interphase)
The ending number of chromosomes is 23 in humans (egg has 23 and sperm has 23). This is haploid (n).

14. How many chromosomes? 38 46 20
200 78

15. Chromosomes in Humans
Somatic cells=46 chromosomes
Diploid (2n) - a cell that contains 2 complete sets of chromosomes
Gametes =23 chromosomes
Haploid (n) - a cell that contains 1 complete set of chromosomes

16. Let’s review
How do we go from one single cell to an multi-cell organism?

17. Why do you think sperm and egg are haploid? (have 23 chromosomes)

18. Oogenesis & Spermatogenesis
After meiosis the cells have a few more steps before they are eggs & sperm
Spermatogenesis: 4 sperms are created after the cell is modified to have flagella
Oogenesis: eggs need more cytoplasm and organelles so the cytoplasm of 3 of the cells is absorbed by 1. This results in 1 large egg cell and 3 polar bodies that get reabsorbed by the body.

19. Spermatogenesis and Oogenesis

20. Meiosis clip https://www. youtube. com/watch
Meiosis clip Stop here Monday.

21. Homologous chromosomes
Chromosomes that share the same gene location for a particular trait

22. Tetrad
- Structure containing 4 chromatids that form during meiosis.

23. Crossing over
Homologous chromosomes exchange portions of their chromatids.
Results in new combinations of genes and different chromatids
Happens in PROPHASE

24. Homologous chromosomes

27. How does Meiosis create genetic diversity?
Why do you look different from your siblings?

28. Can you determine which children belong to which couple
Can you determine which children belong to which couple? Genetic variation is important in creating individuals!
From Pearson Education

29. Answer: The first and last picture belong to couple 1
Answer: The first and last picture belong to couple The middle pictures belong to couple 2.

30. How does meiosis promote genetic variation?
Independent Assortment - Each chromosome is randomly sorted independently of other chromosomes
A human who has 46 chromosomes, there are around 8 million possible combinations for a sperm or egg cell.

31. How does meiosis promote genetic variation?
Crossing Over – pairs of homologous chromosomes swap the same segment of genes, forming a chromosome that has some of mom’s and some of dad’s DNA combined.

32. How does meiosis promote genetic variation?
Random Fertilization – the fertilization of an egg and sperm is completely random

33. 1/5/2018-Find your seat! Complete Mitosis vs. Meiosis Chart
Quiz on MONDAY!!

34. 1/5/2018-Find your seat! Complete Mitosis vs. Meiosis Chart
Quiz on MONDAY!!

35. 1/5/2018-Find your seat! Complete Mitosis vs. Meiosis Chart
Quiz on MONDAY!!

36. 1/5/2018-Find your seat! Complete Mitosis vs. Meiosis Chart
Quiz on MONDAY!!

37. Steps in Meiosis
Meiosis I: Prophase I Metaphase I Anaphase I Telophase I Meiosis II: Prophase II Metaphase II Anaphase II Telophase II

38. Prophase I DNA condenses and chromosomes become visible.
Crossing over occurs

39. Metaphase I
Homologous chromosomes line up along the metaphase plate

40. Anaphase I
Spindle fibers move homologous chromosomes to opposite sides of the cell.

41. Telophase I & Cytokinesis
Nuclear membrane reforms and cytokinesis occurs
Result is two diploid daughter cells.

42. Prophase II
Homologous chromosomes pair and from tetrads.

43. Metaphase II
Chromosomes line up along the equator, not in homologous pairs.

44. Anaphase II
Chromatids separate

45. Telophase II Nuclear membrane reforms; cytoplasm divides
Result is 4 haploid gametes.

46. Cut out cells and place on the Meiosis Steps Chart.
Let me check before you glue down~
Stamp #1-Meiosis Chart
AFTER I have stamped your paper, begin the Color-By-Number!

47. Practice Questions

48. Practice Question
What inference can be made from the diagram shown?
A. The sperm will have double the amount of chromosomes as the parent cell.
B. None of the cells made copies of their chromosomes
C. The sperm will have half the number of chromosomes as the parent cell.

49. The diagram above shows the process of meiosis
The diagram above shows the process of meiosis. The segregation that occurs during meiosis results in a — A decrease in the total number of cells per organism B reduction in the number of chromosomes per cell C group of genetically identical cells

50. Compare to mitosis, Meiosis will result in
A. 2 Daughter cells B. 4 Daughter Cells C. Less number of daughter cells than mitosis

51. What is the name of this process?
Mitosis
DNA replication
Crossing over

52. Which of the following is NOT a result of Crossing over?
Both chromosomes with identical genes
New combination of genes in each chromosome
Genetic variability

53. Which process of Meiosis is represented by “X”?
Mitosis
Meiosis I
Meiosis II