1. Chapter 12: The Cell Cycle (How do cells divide?)
cell division in prokaryotes
chromosomes
eukaryotic cell cycle
mitosis
cytokinesis

2. Prokaryotes
binary fission
generation time as short as 20 minutes

3. Chapter 12: The Cell Cycle (How do cells divide?)
cell division in prokaryotes
chromosomes
eukaryotic cell cycle
mitosis
cytokinesis

4. Describe the human genome and karyotype in terms of:
Define:
chromosome
chromatin
gene
genome
karyotype
Describe the human genome and karyotype in terms of:
number of basepairs
number of genes
number of chromosomes

5. Eukaryotic DNA in chromosomes
chromatin: long DNA molecule with associated proteins
chromosomes: densely packaged chromatin
during cell division
protects the DNA
sets up DNA distribution

6. each chromosome contains hundreds to thousands of genes
functional units of heredity
typically instructions for a protein or RNA
genome – organism’s complete DNA sequence
humans apparently have ~25,000 genes in the now-sequenced human genome

7. chromosomes each species has a characteristic number of chromosomes
number varies between species
does not reflect complexity
humans: 46
some ferns: 1000+
chromosomes for an individual is the karyotype

9. chromosomes
function: chromosomes carry the genetic information of a cell
from one cell generation to the next
from one organism to its offspring

11. Describe the human genome and karyotype in terms of:
Define:
chromosome
chromatin
gene
genome
karyotype
Describe the human genome and karyotype in terms of:
number of basepairs
number of genes
number of chromosomes

12. Chapter 12: The Cell Cycle (How do cells divide?)
cell division in prokaryotes
chromosomes
eukaryotic cell cycle
mitosis
cytokinesis

13. Draw a circle diagram of the eukaryotic cell cycle. Label all phases.
Discuss what goes on in each of the phases on the diagram. Note where checkpoints exist. Also, discuss G0, and discuss cell cycle regulation in general terms.

14. Eukaryotic Cell Cycle
when cells reach a certain size, growth either stops or the cell must divide
cell division is generally a highly regulated process (not all will divide!)
the generation time for eukaryotic cells varies widely, but is usually 8-20 hours

15. Eukaryotic Cell Cycle

16. Eukaryotic Cell Cycle
cyclins and cyclin-dependent protein kinases (Cdks)
cytokinins; growth factors; suppressors; cancer cells

17. Draw a circle diagram of the eukaryotic cell cycle. Label all phases.
Discuss what goes on in each of the phases on the diagram. Note where checkpoints exist. Also, discuss G0, and discuss cell cycle regulation in general terms.

19. Chapter 12: The Cell Cycle (How do cells divide?)
cell division in prokaryotes
chromosomes
eukaryotic cell cycle
mitosis
cytokinesis

20. Describe what “PMAT” means.
With a partner, do the “chromosome dance” for mitosis. Make sure that you distinguish between chromosomes and chromatids, and note at each stage the number of sister chromatids per chromosome.
Discuss what happens in each stage of mitosis.

21. Mitosis
4 stages:
prophase
metaphase
anaphase
telophase
(PMAT) *

22. Mitosis: prophase chromatin condenses to form chromosomes
each chromosome (duplicated during S phase) forms a pair of sister chromatids
sister chromatids are joined at a centromere by protein tethers
centromeres contain a kinetochore where microtubules will bind
each sister chromatid has its own kinetochore
sister chromatids become attached by their kinetochores to microtubules from opposite poles

23. Mitosis: prophase
a system of microtubules, called the mitotic spindle, organizes between the two poles (opposite ends) of the cell
each pole has a microtubule organizing center (MTOC)
in animals and some other eukaryotes, centrioles are found in the MTOC

24. Mitosis: prophase by the end of prophase:
the nuclear membrane has disappeared (actually divided into many small vesicles)
nucleoli have disintegrated
the sister chromatids are attached by their kinetochores to microtubules from opposite poles

25. Mitosis: prophase
some call the later part of prophase prometaphase, usually defined to include vesicularization of the nuclear membrane and attachment of kinetochores to microtubules
in some eukaryotes the nuclear membrane never vesicularizes

26. Mitosis: metaphase
chromosomes line up along the midplane of the cell (the metaphase plate)
chromosomes are highly condensed
the mitotic spindle, now complete, has two types of microtubules
kinetochore microtubules extend from a pole to a kinetochore
polar microtubules extend from a pole to the midplane area, often overlapping with polar microtubules from the other pole
the mitosis checkpoint appears to be here; progress past metaphase is typically prevented until the kinetochores are all attached to microtubules

27. Mitosis: anaphase
sister chromatids separate and are moved toward opposite poles
the protein tethers at the centromere between the chromatids are broken
each former sister chromatid can now be called a chromosome

28. Mitosis: anaphase
model for the mechanism that moves chromosomes to the poles
motor proteins move the chromosomes towards the poles along the kinetochores microtubules
kinetochore microtubules shorten behind the moving chromosomes
polar microtubules lengthen the entire spindle
motor proteins on the polar microtubules slide them past each other, pushing them apart (the microtubules may grow a bit, too)
this pushes the MTOCs away from each other, and thus has the effect of pushing kinetochore microtubules from opposite poles away from each other *

29. Mitosis: anaphase
overall, this process assures that each daughter cell will receive one of the duplicate sets of genetic material carried by the chromosomes

30. Mitosis: telophase prophase is essentially reversed
the mitotic spindle is disintegrated
the chromosomes decondense
nuclear membranes reform around the genetic material to form two nuclei
each has an identical copy of the genetic information
nucleoli reappear, and interphase cellular functions resume *

31. Describe what “PMAT” means.

32. With a partner, do the “chromosome dance” for mitosis
With a partner, do the “chromosome dance” for mitosis. Make sure that you distinguish between chromosomes and chromatids, and note at each stage the number of sister chromatids per chromosome.
Discuss what happens in each stage of mitosis.

33. Chapter 12: The Cell Cycle (How do cells divide?)
cell division in prokaryotes
chromosomes
eukaryotic cell cycle
mitosis
cytokinesis

34. Describe cytokinesis in both plant cells and animal cells, noting the differences.
Describe what is meant by the term “polar division” and why this process was (and still is) important in your development.

35. cytokinesis divides the cell into two daughter cells
cytokinesis usually begins in telophase and ends shortly thereafter

36. cytokinesis in animals, a cleavage furrow develops
usually close to where the metaphase plate was
a microfilament (actin) ring contracts due to interactions with myosin molecules, forming a deepening furrow
eventually, the ring closes enough for spontaneous separation of the plasma membrane, resulting in two separate cells *

37. cytokinesis in plants, a cell plate develops
usually close to where the metaphase plate was
vesicles that originate from the Golgi line up in the equatorial region
the vesicles fuse and add more vesicles
grow outward until reaching the plasma membrane and thus separating the cells
the vesicles contain materials for making the primary cell wall and a middle lamella *

38. cytokinesis
cytoplasm (and with it most organelles) is usually distributed randomly but roughly equally between daughter cells
sometimes cell division is a highly regulated polar division that purposefully distributes some materials unequally

39. Describe cytokinesis in both plant cells and animal cells, noting the differences.
Describe what is meant by the term “polar division” and why this process was (and still is) important in your development.

40. In the following slide, look for examples of interphase, prophase, metaphase, anaphase, and telophase/cytokinesis.

41. *