1. PowerLecture: Chapter 9
How Cells Reproduce

2. Understanding Cell Division
What instructions are necessary for inheritance?
How are those instructions duplicated for distribution into daughter cells?
By what mechanisms are instructions parceled out to daughter cells?

3. Reproduction
Parents produce a new generation of cells or multicelled individuals like themselves
Parents must provide daughter cells with hereditary instructions, encoded in DNA, and enough metabolic machinery to start up their own operation

4. What you will be expected to learn
The purpose and process of cellular reproduction
How different types of cells divide
Why cells divide
The process of the cell cycle
The relationship between nucleic acids, genes and chromosomes
What happens when there are errors in the cycle

5. Division Mechanisms Eukaryotic organisms
Remember me why am I called eukaryotic?
Mitosis
Meiosis
Prokaryotic organisms
Remember me? Why am I called prokaryotic?
Prokaryotic fission

6. Roles of Mitosis Multicelled organisms
Growth
Cell replacement
Some protistans, fungi, plants, animals
Asexual reproduction

7. Chromosome A DNA molecule & attached proteins
Duplicated in preparation for mitosis
one chromosome (unduplicated)
one chromosome (duplicated)

8. Chromosome a One chromosome (unduplicated) one chromatid two sister
chromatids
one chromatid
b One chromosome (duplicated)
Stepped Art
Fig. 9-3a, p.142

9. multiple levels of coiling of DNA and proteins
Chromosome
multiple levels of coiling of DNA and proteins
centromere
(constricted region)
fiber
beads on a string
DNA double helix
core of histone
nucleosome
Fig. 9-4, p.143

10. Organization of Chromosomes
DNA
one nucleosome
DNA and proteins
arranged as cylindrical fiber
histone

11. Organization of Chromosomes
Chromosome structural organization

12. Write a statement that describes the relationship between chromosomes, chromatids, and DNA

13. Chromosome Number Sum total of chromosomes in a cell
Somatic cells (Body cells) give an example
Chromosome number is diploid (2n)
Two of each type of chromosome
Gametes
Chromosome number is haploid (n)
One of each chromosome type

14. Human Chromosome Number
Diploid chromosome number (2n) = 46
n=?
Two sets of 23 chromosomes each
One set from father
One set from mother
Mitosis produces cells with 46 chromosomes--two of each type
Note it is very important that you can distinguish between the two.

15. The Cell Cycle interphase G1 S telophase anaphase Mitosis G2 metaphase
prophase
Figure 9.5 Page 144

16. The Cell Cycle
The cell cycle

17. Interphase Usually longest part of the cycle Cell increases in mass
Number of cytoplasmic components doubles
DNA is duplicated
Why is DNA duplicated before cell division?

18. Mitosis Period of nuclear division
Usually followed by cytoplasmic division
Four stages: Prophase, Metaphase, Anaphase, Telophase

19. Control of the Cycle
Once S begins, the cycle automatically runs through G2 and mitosis
The cycle has a built-in molecular brake in G1
Cancer involves a loss of control over the cycle, malfunction of the “brakes”

20. The Spindle Apparatus Consists of two distinct sets of microtubules
Each set extends from one of the cell poles
Two sets overlap at spindle equator
Moves chromosomes during mitosis

21. Stages of Mitosis (PMAT)
Prophase
Metaphase
Anaphase
Telophase

22. Early Prophase - Mitosis Begins
Duplicated chromosomes begin to condense
Figure 9.7
Page 146

23. Late Prophase New microtubules are assembled
One centriole pair is moved toward opposite pole of spindle
Nuclear envelope starts to break up
Figure 9.7
Page 146

24. Metaphase All chromosomes are lined up at the spindle equator
Chromosomes are maximally condensed
Figure 9.7
Page 147

25. Anaphase Sister chromatids of each chromosome are pulled apart
Once separated, each chromatid is a chromosome
Figure 9.7
Page 147

26. Telophase Chromosomes decondense
Two nuclear membranes form, one around each set of chromosomes
Figure 9.7
Page 147

27. Results of Mitosis Two daughter nuclei
Each with same chromosome number as parent cell
Figure 9.7
Page 147

28. Mitosis
Mitosis step-by-step

29. Cytoplasmic Division
Usually occurs between late anaphase and end of telophase
Two mechanisms
Cell plate formation (plants)
Cleavage (animals)

30. Animal Cell Division

31. Cell Plate Formation

32. Cell Plate Formation
Cytoplasmic division

33. Mitotic Control
Kinases : enzymes that when DNA is defective activate proteins that stop the cell cycle.
Growth factors: promote manufacture of genes that play a role in the organisms growth.
Checkpoint genes: control the cell cycle.

34. Tumors
Sometimes a checkpoint gene mutates and control over cell division is lost.
Cells uncontrollable division forms an abnormal mass called a tumor.

35. Cancer
Cancer and metastasis

36. Cancer benign tumor malignant tumor
1 Cancer cells slip of out their home tissue
2 The metastasizing cells
become attached to the wall
of a blood or lymph vessel.
They secrete digestive
enzymes onto it. Then they
cross the wall at the breach.
3 Cancer cells creep or
tumble along inside blood
vessels, then leave the
bloodstream the same way
they got in. They start new
tumors in new tissues.
Fig. 9-13, p.151

37. What type of energy is used for cell division?