1. Chapter 8 Biology CPA Thank you, Miss Colabelli!
Cell Reproduction
Chapter 8
Biology CPA
Thank you, Miss Colabelli!

2. Chromosomes Rod shaped structures made of DNA and proteins
Chromosomes are visible in cells undergoing division
Chromosomes are made by DNA coiling into tight structures
Consist of two identical halves

3. Chromosome Structure
Histones are proteins that DNA wraps around to make the chromosome shape
Chromosomes are made of two sister chromatids
Identical to each other

4. Chromosome Structure
Each chromosome is made of two “sister” chromatids
Near center of the chromosome is the centromere
Chromosomes are tightly coiled strings of DNA called chromatin

5. Chromosome Numbers
There is a specific number of chromosomes in each organism
Ex: Humans have 46, chimpanzees have 48
Humans have autosomes and sex chromosomes
We have 2 sex chromosomes
Either X or Y
We also have 44 autosomes
Which do not code for gender

6. Chromosome Numbers
Every cell of an organism produced by sexual reproduction has two copies of each autosome
One copy from mom and one copy from dad
The two copies of each pair is called homologous chromosomes
Same size and shape
Carry genes for the same traits

7. Karyotype A karyotype is a picture of one set of chromosomes
Shows you sex of organism
Shows your any chromosomal disorders

8. Chromosome Numbers A diploid cell contains 2 sets of each chromosome
Prefix di = 2
Abbreviated as 2n
n = number of chromosomes
A haploid cell contains only 1 set of each chromosome
Half of the total number
Usually sex cells

9. Cell Division in Prokaryotes
No nucleus
No organelles
Ex: Bacteria
Reproduction is very fast
Copy DNA
Split into two identical daughter cells
Cell division is called binary fission

10. Cell Division in Eukaryotes
Have a nucleus
Have organelles
Ex: Humans, plants
Both nucleus and cytoplasm need to divide
Process of making new cells is called mitosis
Makes two identical daughter cells
Complex reproduction
Everything needs to be regulated!
Much more complex process – about 18 hours!

11. Cell Division and Reproduction
Asexual Reproduction
Produces identical offspring from a single parent
Used by many single-celled organisms
Ex: bacteria
Occurs very quickly
Sexual Reproduction
Produces genetically different offspring from two parents
Fusion of two parent cells
Creates haploid gametes (sex cells)

12. The cell Cycle A repeating set of events in the life of a cell
A cell splits to make 2 identical copies
This occurs in 3 main stages
Interphase – growth
Mitosis – division of the cell
Cytokinesis – Splitting of the cytoplasm

13. Interphase Cell growth
Majority of cell’s life span is spent in this phase
3 Part of Interphase:
G1, S, G2

14. G1 Phase
Gap 1 Phase
The cell is growing to mature size

15. S Phase S = synthesis of DNA
DNA is copied so there is a set for each new cell

16. G2 Phase Gap 2 Phase Cell grows again Replication of organelles
Cell prepares for cell division

17. mitosis
Cell Division

18. mitosis
The part of a cell’s life cycle when the cell’s nucleus divides into 2 identical nuclei
4 steps:
Prophase
Metaphase
Anaphase
Telophase

19. Prophase Shortening and tight coiling of chromatin into chromosomes
Nucleus breaks down and disappears
Centrioles separate and move to opposite poles of the cell
Centrosomes in plant cells
Centrioles shoot off spindle fibers

20. metaphase Spindle fibers are connected to centromere of chromosomes
Spindle fibers move chromosomes
Chromosomes line up at the equator of the cell
Chromosomes are in the MIDDLE

21. anaphase Sister chromatids attach to the short spindle fibers
Chromatids of each chromosome separate at the centromere
Chromosomes are pulled APART
Spindle fibers shorten and bring the sister chromatids to opposite poles
After chromatids separate, they are called individual chromosomes

22. Telophase Chromatids become chromatin Spindle fibers disassemble
Nuclear envelope forms around each set of chromatin
Nucleolus reappears

23. Cytokinesis Once mitosis has finished! Last stage of cell cycle
Process is when the cytoplasm splits apart

24. Cytokinesis in Plant Cells
A cell plate forms between the two nuclei
The cytoplasm divides
A cell wall forms two daughter cells

25. Cytokinesis in Animal Cells
Cell membrane pinches in at equator
Cleavage furrow

26. Cells in Various Stages of the Cell Cycle

27. Control of Cell Division
Checkpoints (Regulatory Proteins)
Repair enzymes fix any mutations
G1 Checkpoint
Proteins check to see if cell will be able to divide
Check for cell size
G2 Checkpoint
DNA repair enzymes check results of DNA replication during S phase
Mitosis checkpoint
If all is correct, proteins will signal cell to exit mitosis
Cell will renter interphase after cytokinesis and start process over again
If a cell does not meet requirements for checkpoints, the cell will be programmed to die
Apoptosis is controlled cell death

28. The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases
Two types of regulatory proteins are involved in cell cycle control: cyclins and cyclin-dependent kinases (Cdks)
Cdks activity fluctuates during the cell cycle because it is controled by cyclins, so named because their concentrations vary with the cell cycle
MPF (maturation-promoting factor) is a cyclin-Cdk complex that triggers a cell’s passage past the G2 checkpoint into the M phase

29. (b) Molecular mechanisms that help regulate the cell cycle
Figure 12.17 M G1 S G2 M G1 S G2 M G1
MPF activity
Cyclin concentration
Time
(a) Fluctuation of MPF activity and cyclin concentration during the cell cycle G1 S
Cdk
Figure Molecular control of the cell cycle at the G2 checkpoint.
Cyclin accumulation
Degraded cyclin M G2
G2 checkpoint
Cdk
Cyclin is degraded
Cyclin
MPF
(b) Molecular mechanisms that help regulate the cell cycle

30. Stop and Go Signs: Internal and External Signals at the Checkpoints
An example of an internal signal is that kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase
Some external signals are growth factors, proteins released by certain cells that stimulate other cells to divide
For example, platelet-derived growth factor (PDGF) stimulates the division of human fibroblast cells in culture

31. A clear example of external signals is density-dependent inhibition, in which crowded cells stop dividing
Most animal cells also exhibit anchorage dependence, in which they must be attached to a substratum in order to divide
Cancer cells exhibit neither density- dependent inhibition nor anchorage dependence

32. Density-dependent inhibition
Figure 12.19
Anchorage dependence
Density-dependent inhibition
Density-dependent inhibition
Figure Density-dependent inhibition and anchorage dependence of cell division.
20 m
20 m
(a) Normal mammalian cells
(b) Cancer cells

33. Loss of Cell Cycle Controls in Cancer Cells
Cancer cells do not respond normally to the body’s control mechanisms
Cancer cells may not need growth factors to grow and divide
They may make their own growth factor
They may convey a growth factor’s signal without the presence of the growth factor
They may have an abnormal cell cycle control system

34. A normal cell is converted to a cancerous cell by a process called transformation
Cancer cells that are not eliminated by the immune system, form tumors, masses of abnormal cells within otherwise normal tissue
If abnormal cells remain at the original site, the lump is called a benign tumor
Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form additional tumors

35. A tumor grows from a single cancer cell.
Figure 12.20
Lymph vessel
Tumor
Blood vessel
Cancer cell
Glandular tissue
Metastatic tumor 1
A tumor grows from a single cancer cell. 2
Cancer cells invade neighboring tissue. 3
Cancer cells spread through lymph and blood vessels to other parts of the body. 4
Cancer cells may survive and establish a new tumor in another part of the body.
Figure The growth and metastasis of a malignant breast tumor.

36. Compare/Contrast