1. Standard 2
Cell Division
“Chromosome Waltz”

2. Chromosome Condensed form of chromatin
a threadlike structure of nucleic acids and protein
Always paired with an identical copy of itself

3. CHROMATID
Chromosome
SISTER CHROMATIDS

4. Chromosome

5. Types of Chromosomes Y X Autosomes
The 1st 22 pairs of Chromosomes in humans.
Sex Chromosomes
23rd pair
In females, the sex chromosomes are the 2 X chromosomes.
Males have one X chromosome and one Y chromosome.
The Y chromosome is what makes a baby boy. X Y

6. Types of Cell Division Asexual: Offspring are identical to parents
Examples:
Budding: yeast
Binary Fission: bacteria
Sexual: Offspring have a combination of genetic information from 2 parents
(Sperm and Egg)
Ex: Animals and Plants

7. Why do cells divide? Growth Reproduction (Development)
Repair or Replace

8. What Happens in Cell Division
Replicates the DNA exactly.
Movement of the two copies of DNA to opposite ends of the cell.
Separates into two daughter cells.

10. Mitosis (1 cell becomes 2)
both new cells are identical to the original
(all cells except sperm & eggs do this)

11. Cell Cycle Interphase 90% of cell cycle Three phases G1- Growth
Chromosomes appear as threadlike coils (chromatin)
90% of cell cycle
Three phases
G1- Growth
S- DNA Replication
G2- Growth (prepares to divide)

12. Mitosis 4 stages Prophase Metaphase Anaphase Telophase PMAT
Cell division occurs in a series of stages, or phases.
4 stages
Prophase
Metaphase
Anaphase
Telophase
PMAT

13. Prophase "BEFORE" Mitosis begins (cell begins to divide)
You can see chromosomes start to form
Late
Early

14. Chromosomes line up in the center of the cell
Metaphase
"MIDDLE"
Chromosomes line up in the center of the cell

15. Anaphase
"ANTI"
Chromatids or chromosomes separate and begin to move to opposite ends of the cell

16. Chromosomes appear as chromatin Mitosis ends
Telophase
"TWO"
Two new nuclei form
Chromosomes appear as chromatin Mitosis ends

17. Cytokinesis Become two identical new cells
"Split"
Become two identical new cells
Half the size of the original

18. Metaphase Interphase Prophase Anaphase Telophase
What Stages of Mitosis can you find?

19. Mitosis Meiosis What looks similar between mitosis and meiosis?
What looks different?
Prophase
Interphase
Mitosis
Cytokinesis
Telophase
Metaphase
Anaphase
Meiosis

20. Meiosis- The process in which gametes (sex cells) are made.

21. 1 cell becomes 4 cells called gametes
Meiosis
1 cell becomes 4 cells called gametes
Male gametes = Sperm
Female gametes = Eggs

22. Cells in your body include…
Somatic cells: Make up the various parts of your body including tissues and organs.
Diploid cells (Full set of 23 chromosome pairs)
Gametes: sex cells – eggs in females and sperm in males.
Haploid cells
(1/2 required # chromosomes)

23. Meiosis is Mitosis twice
The Difference?
Meiosis is Mitosis twice
without
Interphase in between
&
Mitosis is in my Toes, but
Meiosis is in my Ovaries

24. Why Meiosis? Number of Fertilization Chromosomes
Union of sperm and egg (n)
Zygote is formed (2n)
The chromosome number is reduced, so at fertilization there is the correct # of chromosomes.

25. Why meiosis? Cuts chromosome # in half Creates variation for Evolution
Makes offspring unique

26. Meiosis creates variation in 3 ways
1) Law of Segregation
chromosome pairs separate during meiosis
2) Law of independent assortment genes are separated randomly (shuffle)
3) Crossing Over
chromosome parts break off & reattach to other chromosomes creates new chromosome

27. Mitosis (1 cell becomes 2)
both new cells are identical to the original
(all cells except sperm & eggs do this)

28. 1 cell becomes 4 cells called gametes
In Meiosis…
1 cell becomes 4 cells called gametes
Male gametes = Sperm
Female gametes = Eggs
Mitosis is in my Toes, but
Meiosis is in my Ovaries

29. Mitosis or Meiosis Haploid (N) Diploid (2N)
Cells with 2 full sets of genetic info
Human body cells have 46 chromosomes each
(diploid or 2N # is 46)
Haploid (N)
Cells with 1 set of genetic info
Human sperm & eggs have 23 chromosomes
(haploid or N # is 23)

30. Meiosis Mitosis Makes haploid cells Makes diploid cells
Why ---Importance:
Meiosis
Makes haploid cells
Makes genetically different cells
Takes place at certain times
Males: after puberty
Females: Before birth
Mitosis
Makes diploid cells
All cells identical
Involved in somatic cell reproduction.
Happens ALL your life

32. Stages of Meiosis Interphase Prophase I Metaphase I Anaphase I
Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II

33. Interphase
Interphase is the same as Mitosis.
G1, S phase and G2.

34. Prophase I Same as Mitosis…except:
Each pair of sister chromosomes matches with another set of sister chromosomes.
Forms a tetrad- 2 sets of chromosomes (4 chromatids).
This step is when crossing over occurs!!!!

35. Metaphase I
The tetrads line up at the center of the cell.

36. Anaphase I
Tetrads separate into chromosomes and move to opposite ends of the cell.

37. Telophase I
The chromosomes uncoil and the cell begins to break into two cells.
Still too many chromosomes, so the cells goes through another 4 stages.

38. STOP!! There is NO interphase II in meiosis… Why??
No need to replicate the DNA again…. We’re making haploid cells with only HALF the required DNA.

39. Prophase II Chromosomes coil and thicken.
Nuclear envelopes break down.

40. Metaphase II
Chromosomes line up at the center of the cell.

41. Anaphase II
Chromosomes separate and the chromatids move to opposite ends of the cell.

42. Telophase II
The chromatids uncoil and lengthen, and the cell breaks into two cells.
Four gametes have been made
They are haploid cells (half necessary DNA).

43. Meiosis Anaphase 1 Anaphase 2 Interphase (approx 90% of time)
DNA Replication
Prophase 1 Tetrad forms
Crossing over occurs
Metaphase 1
Chromosomes move to midline
Anaphase 1
Homologous chromosomes separate
Anaphase 2
Sister chromatids separate
The Rest is Just Like Mitosis!

45. Chromosomes How do we look at the chromosomes of an individual?
The collection of chromosomes found in an individual’s cells
Karyotype

46. Chromosomes How is it made?
Chemically treat and stain chromosomes in cells from a blood sample
The chromosomes are then photographed, cut out, arranged in pairs from largest to smallest, and numbered

47. Chromatin
Chromosome Scatter
Karyotype

48. Chromosomes Abnormalities
Nondisjunction (NOT-COMING-APART)
Chromosomes fail to separate during anaphase
2. Mutations: changes in Chromosome Structure

49. Nodisjunctions What if a chromosome is missing?
Most do not survive to be born
If a chromosome is missing the condition is called Monosomy
EX: Turners (XO)

50. Nondisjunctions
What if a cell has an extra chromosome?
The condition in which a cell has an extra chromosome is called Trisomy
Example: Trisomy 21
(Down Syndrome)

51. Chromatids do not Separate in Anaphase II
Nondisjunction
TRISOMY
MONOSOMY
NORMAL X x l
Chromatids do not Separate in Anaphase II

52. Mutations Deletion part of the chromosome breaks off
Duplication: part of the chromosome is repeated

53. Cancer
Mutations in genes that control normal cell division can lead to cancer.
Increasing your risk
Sun without sun block
Smoking or being around 2nd hand smoke
Working with known cancer causing chemicals.

54. Proto-Oncogenes are normal genes that code proteins involved in a cell's normal growth
Oncogenes tell cells to make proteins that cause excessive cell growth and division.
*Oncogenes are Mutant Forms of Proto-Oncogenes*

55. Why don’t we all get cancer?
Tumor Suppressor Genes
Normal genes whose ABSENCE can lead to cancer.
Why don’t we all get cancer?
Genes come in pairs, one from each parent
A defect in one copy will not cause cancer because the other normal copy is still functional.