1. The Cell Cycle

2. Limits to Cell Growth Living things grow by producing MORE cells
Your body is constantly making new cells
The life cycle of a cell is called the cell cycle

3. Limits to Cell Growth
2 main reasons that cells divide rather than continuing to grow indefinitely:
The larger the cell, the more demands it places on its DNA
The larger, the more problematic transport becomes into/out of the cell

4. The Cell Cycle Begins: when the cell is formed
Ends: once the cell has divided and has formed new cells

5. The Cell Cycle

6. The Cell Cycle
DNA organized into chromosomes (found in the nucleus)

7. The Cell Cycle
DNA organized into chromosomes (found in the nucleus)
During the cell cycle the cell must copy DNA (found in chromosomes) to pass onto the newly formed cell

8. The Cell Cycle Prokaryotic cells: Bacteria Binary fission
“splitting into 2 parts”

9. The Cell Cycle
Binary Fission

10. The Cell Cycle Eukaryotic cells:
Chromosomes contain more DNA than in prokaryotic cells

11. The Cell Cycle
Eukaryotic cells:
All body cells in organism have same number of chromosomes and exactly the same DNA
Humans have 46 chromosomes!

12. The Cell Cycle Eukaryotic cells:
most organisms have chromosomes in matching pairs - one from each parent- called homologous chromosomes
Humans have 23 pairs !

13. Homologous Chromosomes

14. The Cell Cycle Three Stages
interphase: cell grows and copies organelles & chromosomes
-longest phase of cycle
-divided into 3 stages

15. The Cell Cycle Three Stages Interphase:
G1 - growing; increase in size; make new organelles & proteins
S - replication of chromosomes
G2 - cell division molecules produced

16. The Cell Cycle Interphase:
In a cell that is not dividing, the DNA is in the nucleus and is in long, tangled strands called chromatin
When a cell gets ready for division (mitosis), DNA must get organized!

17. The Cell Cycle Interphase: Think of DNA like thread.
As chromatin the thread is all tangled.
As a chromosome, the DNA is all wound up and organized, like thread on a spool.

18. Structure of a Chromosome
Each side of 'X' is
a chromatid
Each chromatid is
identical in the
information it
contains - replicated DNA

19. Structure of a Chromosome
The center
structure that holds
2 sister chromatids
together is called a
centromere

20. Structure of a Chromosome

21. The Cell Cycle Three Stages
2. Mitosis: chromatids separate and 1 cell divides into 2
Each cell has a nucleus with the same number of chromosomes
Divided into 4 stages

22. Mitosis (cell division)
Prophase
Metaphase
Anaphase
Telophase

23. The Cell Cycle Mitosis Prophase Nuclear membrane dissolves
Chromatin condense into chromosomes
Centrioles separate (opposite poles) and form spindle fibers

24. The Cell Cycle
Mitosis
prophase

25. The Cell Cycle
Mitosis
prophase

26. The Cell Cycle Mitosis Metaphase
Homologous chromosomes pair up at the equator
Connected to spindle fibers at centromere

27. The Cell Cycle
Mitosis
metaphase

28. The Cell Cycle
Mitosis
metaphase

29. The Cell Cycle Mitosis Anaphase
Sister chromatids separate into individual chromosomes and move to opposite poles of cell

30. The Cell Cycle
Mitosis
anaphase

31. The Cell Cycle
Mitosis
anaphase

32. The Cell Cycle Mitosis Telophase
Nuclear membrane forms around each set of chromosomes & they unwind

33. The Cell Cycle
Mitosis
telophase

34. The Cell Cycle
Mitosis
telophase

35. Can you identify the stages?

36. The Cell Cycle Three Stages
3. Cytokinesis: the division of the cytoplasm
two new cells
(daughter cells)
each identical

37. The Cell Cycle Cytokinesis: -animal cells: pinched
-plant cells: form a cell plate