1. Chapter 13:The Cell Cycle
Adapted from: Kim Foglia

2. How did you get from there to here?
And now look at you…
How did you get from there to here?

3. Getting from there to here…
Cell division
continuity of life = reproduction of cells
reproduction
unicellular organisms
growth
repair & renew
Cell cycle
life of a cell from origin to division into 2 new daughter cells
Unicellular organisms
Cell division = reproduction
Reproduces entire organism& increase population
Multicellular organisms
Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg
Also use cell division to repair & renew cells that die from normal wear & tear or accidents

4. A bit about DNA DNA is organized in chromosomes
double helix DNA molecule
associated proteins = histone proteins
Nucleosome = a segment of DNA wrapped around 8 histone proteins
DNA-protein complex = chromatin
organized into long thin fiber

6. Chromosome Duplicated chromosome consists of 2 sister chromatids
meet at the centromere
contain identical copies of the chromosome’s DNA
Telomeres = repeated sequence at end of each arm
p= short arm; q= long arm
Centromeres are segments of DNA which have long series of tandem repeats = 100,000s of bases long. The sequence of the repeated bases is quite variable. It has proven difficult to sequence.

8. Prokaryotic Chromosome Structure
Bacteria have a one single loop of DNA

9. Types of Cells & Ploidy Levels
There are two types of human cells: somatic cells and gametes.
Somatic Cells = body cells (brain, muscle, heart, liver, skin, etc)
Contain 46 chromosomes in humans
Diploid (2n)= cell that contains two sets of homologous chromosomes
23 PAIRS of homologous chromosomes = 46 TOTAL chromosomes
Gametes = sex cells (sperm or egg)
Contain 23 chromosomes in humans
Haploid (n)= cell that contains one set of chromosomes

10. Fertilization
When sperm meets egg a zygote is formed. A zygote is the first cell of the embryo. Which of the cells above are haploid (n)? Diploid (2n)?

11. Homologous Chromosomes
Chromosomes containing the same type of genetic information
one comes from male parent, one comes from female parent
DAD
MOM

12. Homologous Chromosomes

13. The chromosomes diagrammed below are arranged in a karyotype, the 46 chromosomes have been arranged in homologous pairs.

14. The first 22 pairs of homologous chromosomes are called autosomes or autosomal chromosomes.
The 23rd pair of chromosomes determines the sex of the individual and are called
sex chromosomes.
The sex chromosomes of a female are XX.
The sex chromosomes of a male are XY.

15. What’s the difference?

16. Cell cycle Cell has a “life cycle”
cell is formed from a mitotic division
cell grows & matures
to divide again
cell grows & matures to never divide again
G1, S, G2, M
liver cells G0
epithelial cells, blood cells,
stem cells
brain nerve cells

17. Cell Division cycle Phases of a dividing cell’s life interphase
cell grows
replicates chromosomes
produces new organelles & biomolecules
mitotic phase
cell separates & divides chromosomes
mitosis
cell divides cytoplasm & organelles
cytokinesis

18. Control of Cell Cycle

19. Interphase 90% of cell life cycle Characteristics
cell doing its “everyday job”
produce RNA, synthesize proteins
prepares for duplication if triggered
Characteristics
nucleus well-defined
DNA loosely packed in long chromatin fibers

20. Interphase Divided into 3 phases: G1 = 1st Gap S = DNA Synthesis
G2 = 2nd Gap

21. Interphase G1 – First stage after division
Cell recovers from previous division
Cell increases in size
Doubles organelles
Accumulates materials for DNA replication
Cells do everyday jobs
G0 – Some cells don’t complete the cycle (nerve and heart muscle)
Continue normal cell operations
No preparation for cell division
Cells will operate in this stage until organism dies
9.1

22. Interphase S Stage – DNA synthesis occurs
At the beginning it contains chromosomes containing one DNA strand
At the end each chromosome contains two identical strands of DNA
Copies chromosomes
G2 – Growth & final preparations for division
Prepares for division
Ends with mitosis
Proteins that aid in mitosis are made in this stage
Microtubules
Nucleus well-defined
DNA loosely packed
9.1

23. Interphase Nucleus well-defined Prepares for mitosis
chromosome duplication complete
DNA loosely packed in long chromatin fibers
Prepares for mitosis
produces proteins & organelles

24. Mitosis copying cell’s DNA & dividing it between 2 daughter nuclei
Mitosis – division of the nucleus
is divided into 5 phases
Prophase
Prometaphase
metaphase
anaphase
telophase

25. Overview

26. Prophase Chromatin (DNA) condenses visible as chromosomes
chromatids
fibers extend from the centromeres
Centrioles move to opposite poles of cell
Fibers (microtubules) cross cell to form mitotic spindle
actin, myosin
Nucleolus disappears
Nuclear membrane breaks down

27. Prometaphase Proteins attach to centromeres
creating kinetochores
Microtubules attach at kinetochores
connect centromeres to centrioles
Chromosomes begin moving

28. Kinetochore Each chromatid has own kinetochore proteins
microtubules attach to kinetochore proteins

29. Metaphase Spindle fibers align chromosomes along the middle of cell
meta = middle
metaphase plate
helps to ensure chromosomes separate properly
so each new nucleus receives only 1 copy of each chromosome

31. Anaphase Sister chromatids separate at kinetochores
move to opposite poles
pulled at centromeres
pulled by motor proteins “walking”along microtubules
increased production of ATP by mitochondria
Poles move farther apart
polar microtubules lengthen

32. Separation of chromatids
In anaphase, proteins holding together sister chromatids are inactivated
separate to become individual chromosomes
1 chromosome
2 chromatids
2 chromosomes

33. Chromosome movement
Kinetochores use motor proteins that “walk” chromosome along attached microtubule
microtubule shortens by dismantling at kinetochore (chromosome) end
Microtubules are NOT reeled in to centrioles like line on a fishing rod.
The motor proteins walk along the microtubule like little hanging robots on a clothes line.
In dividing animal cells, non-kinetochore microtubules are responsible for elongating the whole cell during anaphase, readying fro cytokinesis

34. Telophase Chromosomes arrive at opposite poles Spindle fibers disperse
daughter nuclei form
nucleoli from
chromosomes disperse
no longer visible under light microscope
Spindle fibers disperse
Cytokinesis begins
cell division

35. Cytokinesis Animals cleavage furrow forms
ring of actin microfilaments forms around equator of cell
myosin proteins
tightens to form a cleavage furrow, which splits the cell in two
like tightening a draw string
Division of cytoplasm happens quickly.

36. Cytokinesis in Animals
(play Cells Alive movie here)

37. Mitosis in whitefish blastula

38. Mitosis in animal cells

39. Cytokinesis in Plants Plants
vesicles move to equator line up & fuse to form 2 membranes = cell plate
derived from Golgi
new cell wall is laid down between membranes
new cell wall fuses with existing cell wall

40. Cytokinesis in plant cell

41. Mitosis in plant cell

42. onion root tip