1. The Cell Cycle
Honors: Chapter

2. 2 main parts to the cell cycle
1. Interphase
2. Cell Division
(AKA--Mitotic Phase)

3. Parts of a Homologous Pair of Chromosomes
Centromere
Chromatid
Homologous
Chromosomes

4. Part 1.
INTERPHASE G1 S G2
3 Stages:

5. C E L
C Y C L E
Interphase
Period of cell growth and development that precedes mitosis and follows CYTOKINESIS (cell splitting)
Longest phase of the cell cycle.

6. C E L C Y C L E Interphase G1 = Growth 1—most cell growth
S = Synthesis—cell makes a copy of its DNA
G2 = Growth 2—cell grows a little to prepare for division

7. 2 main parts to the cell cycle
1. Interphase
2. Cell Division
(AKA--Mitotic Phase)

8. Part 2.
MITOSIS & Cytokinesis
Cell Division P M A T
4 Stages:

9. **MITOS I S **
PROPHASE
Chromatin condense & thicken – now called chromosome.
The nuclear envelope breaks down
Centrioles move to opposite "poles“ (or ends) of the cell

10. **MITOS I S ** METAPHASE The spindle (centriole) fully develops.
The chromosomes align at the metaphase plate (middle)

11. **MITOS I S **
Paired chromosomes separate & begin moving to opposite ends (poles) of the cell.
Spindle fibers lengthen & elongate the cell.
Each pole contains a complete set of chromosomes.
ANAPHASE

12. **MI TOS I S ** TELOPHASE Nucleus begins to form at opposite poles.
The nuclear envelopes and nucleoli also reappear.

13. Last Event!!!
CYTOKINESIS

14. C Y T O K I N E S I S CYTOKINESIS
= the division of the original cell's cytoplasm.
(There are now two separate cells)

15. -Write the Stage/Phase BIG!!!
MITOSIS INDEX CARDS
Blank Side:
-Illustration
-Description
Lined Side:
-Write the Stage/Phase BIG!!!

16. Mitosis At the end of Interphase Telophase Metaphase Anaphase Prophase

17. Plant Cell vs. Animal Cell
C Y T O K I N E S I S
CYTOKINESIS:
Plant Cell vs. Animal Cell

18. MITOSIS CELL CYCLE Interphase Cell Division= Mitosis + Cytokinesis
Prophase
Metaphase
Anaphase
Telophase
Interphase
Cell Division= Mitosis + Cytokinesis

19. Do You Know the Stages of Mitosis?C E L
C Y C L E
Do You Know the Stages of Mitosis?
CYTOKINESIS
TELOPHASE
ANAPHASE
PROPHASE
INTERPHASE
METAPHASE
ANAPHASE

20. Overview of the Cell Cycle

21. So why do our cells need to divide??
C Y C L E
So why do our cells need to divide??
To heal any injuries
For growth
Replace lost or damaged cells

22. C E L C Y C L E Cell Cycle Regulation
Cell growth and division are carefully controlled.
Not all cells will go through the cell cycle at the same rate.
Examples of cells NOT dividing often:
Examples of cells
rapidly dividing:
Skin cells
RBC
Nerve
cells
Muscle cells
Bone
marrow
Digestive
tract cells

23. CANC E R What happens if cells LOSE the
ability to CONTROL the cell cycle?

24. CANC E R Cancer = uncontrolled cell growth
. . . cancer cells do NOT respond to regulator signals
. . . results in masses of cells called tumors
. . . cancer = a disease of the cell cycle

25. What Causes Cancer? CANC E R Gene changes due to: diet tobacco use
exposure to radiation
exposure to chemicals
Inherited genes (cyclins/growth factors don’t work)
Immune System Failure
Carcinogens

26. MEIOS I S Now we will look at how our sex cells are made. -Sperm & Egg
What is the difference between a
‘sex cell’ and a ‘body cell?’

27. MEIOS I S Sex Cell Body Cell
Sex cells have ½ the number of chromosomes of body cells
“n”
AKA: gamete
AKA: haploid
Body cells have twice the number of chromosomes as sex cells
2 “n”
AKA: somatic
AKA: diploid

28. MEIOSIS GAMETE FORMATION
GAMETES= SEX CELLS
Female Gamete= EGG
Male Gamete= Sperm

29. MEIOS I S
To create cells with ½ the genetic material you need to have a special process.
This process, called MEIOSIS, occurs in the testes (men) and ovaries (females) in humans.

30. LET’s COMPARE!! M & M
MEIOS I S

31. 2 main parts to the cell cycle of SEX cells :
1. Interphase
2. Meiosis
(AKA--Mitotic Phase)

32. Part 1.
INTERPHASE G1 S G2
3 Stages:

33. WHAT HAPPENS DURING INTERPHASE????C E L
C Y C L E
Interphase
Interphase in all cells is the same. So, all you have to do is remember what you already know…
WHAT HAPPENS DURING INTERPHASE????

34. C E L C Y C L E Interphase G1 = Growth 1—most cell growth
HOMOLOGOUS PAIR- each chromosome that came from dad (orange) has a corresponding chromosome from mom (red)
G1 = Growth 1—most cell growth
S = Synthesis—cell makes a copy of its DNA
G2 = Growth 2—cell grows a little to prepare for division
At the end of interphase each chromosome consist of two identical sister chromatids attached at their centromeres.

35. 2 main parts to the cell cycle of SEX cells :
1. Interphase
2. Meiosis
(AKA--Mitotic Phase)

36. Part 2.
MEIOSIS I
&
MEIOSIS II
MEIOSIS

37. MEIOSIS I

38. **M E I O S I S **
MEIOSIS I
The first part of Meiosis (called Meiosis I) is responsible for reducing the chromosome number by 1/2.
This part consists of 4 phases:
a. Prophase I (crossing over)
b. Metaphase I (independent assortment)
c. Anaphase I
d. Telophase I
& Cytokinesis

39. **M E I O S I S ** PROPHASE I
Prophase I is the longest and most complex phase.
All of the events that occurred during prophase of mitosis occur PLUS…
Homologous chromosomes come together to form a TETRAD.
CROSSING-OVER occurs.

40. ** Exchanging of alleles**
**M E I O S I S **
PROPHASE I
CROSSING OVER:
Portions of 1 chromatid breaks off and attaches to an adjacent chromatid on the homologous pair.
** Exchanging of alleles**
TETRAD
This INCREASES variability within a species!!!!

41. *MEI OS I S *
LET’s COMPARE!! M & M

42. There are 2 major events:
**M E I O S I S **
There are 2 major events:
1) Homologous
chromosomes line up in the Middle of the cell… RANDOMLY= independent assortment (helps to mix up the genetic material)
2) Each centromere becomes attached to a spindle fiber.
METAPHASE I

43. *MEI OS I S *
LET’s COMPARE!! M & M

44. **M E I O S I S ** ANAPHASE I
Homologous chromosomes separate and move towards the poles.
The sister chromatids remain attached at their centromeres.

45. **M E I O S I S ** TELOPHASE I
-Telophase I is the last step in meiosis I. (just like mitosis).
-Following Telophase I..
Cytokinesis occurs and 2 haploid daughter cells are formed.

46. *MEI OS I S *
LET’s COMPARE!! M & M

47. **M E I O S I S ** MEIOSIS I RECAP
Q: What is the purpose of Meiosis I?
A: To decrease the # of chromosomes by 1/2
Q: What 2 features of Meiosis I increase the diversity of the daughter cells?
A: Crossing Over & Independent Assortment

48. MEIOSIS II

49. The steps of Meiosis II are IDENTICAL to Mitosis.**
MEIOSIS II
Meiosis II comes directly after cytokinesis.
No growth (interphase) takes place.
Meiosis II is broken into 4 events:
prophase II
metaphase II
anaphase II
telophase II.
The steps of Meiosis II are IDENTICAL to Mitosis.

50. **M E I O S I S **
MEIOSIS II

51. Meiosis I What happens here?? What happens here??
Interphase
What happens here??
What happens here??
Prophase I
Metaphase I
What type of cell am I??
Anaphase I
Telophase I
Cytokinesis
Images from:

52. Meiosis II Coming from Meiosis I Prophase II Metaphase II Telophase II
Anaphase II
Cytokinesis
Images from:

53. MEIOSIS Coloring Activity**
MEIOSIS Coloring Activity
Material:
Coloring Activity Handout
4 colored pencils (different colors)
Pen/Pencil
Key:
= Dad’s Chromosomes = Mom’s chromosomes
= Nuclear Envelope = Centrioles & Spindles