1. How Cells Reproduce
Chapter 8

2. What is the purpose of reproduction?
Grow in size
Repair old and worn out cells
Replace
Reproduce

3. New cell has to be… An exact copy of the parent cell
i.e. the nuclear material identical to parent
Why?
The chromosomes in nucleus is the control center of the cell
So the chromosome numbers and types of daughter cell HAS to be identical to parent.

4. Cell Cycle
Process of events which a cell is born, carries out its activities and reproduces to make a cell identical to it.
Cycle starts when a new cell forms
During cycle, cell increases in mass and duplicates its chromosomes
Cycle ends when this cell divides

5. So what is a chromosome? Chromosome A B
A double stranded linear DNA molecule associated with proteins.
In a non-dividing cell, it would look like diagram A and is called chromatin
In a cell getting ready to divide, it will look an X and is called a chromosome
Chromosome

7. Chromosmes vs chromatin
Chromosomes
Tightly packed DNA
Found only during cell division
DNA not being used to make proteins
Chromatin
Unwound DNA
Found during Interphase
DNA being used to synthesize proteins and/or replicating

8. Stages of Cell Cycle

9. Cell Cycle Two main phases Interphase Cell division
G1 (growth/generation/gap)
S (synthesis of DNA) G2
Cell division
Mitosis
Cytokinesis

10. Interphase Longest part of the cycle Cell increases in mass
Number of cytoplasmic components increases
Cell develop carry out functions
DNA is duplicated

11. Generation/Growth 1 Phase right after cell division Cell grows in size
Organelles are made if necessary
Cell carries out its functions
Example? ________________
At the end of G1, the cell makes a decision
“To divide or not to divide”

12. Growth 0 Cells will not divide
Will carry out the functions it was meant to perform
Why is that important?
______________

13. Synthesis (S) Cell has made a decision to divide
The chromosomes/DNA will now make exact copies of each other
Amount of DNA doubles by the end of this phase

14. Generation/Growth 2 Cell gets ready for cell division
Makes organelles and proteins necessary for cell division
Spindle fibers
Centrioles

15. Prokaryotic organisms
Division Mechanisms
Eukaryotic organisms
Mitosis
Meiosis
Prokaryotic organisms
Prokaryotic fission

16. Cell division
Mitosis separates the replicated chromosomes into two equal groups
Cytokinesis builds the cell membrane between the two nucleii
The Rutgers Lessons

17. Cell Division Period of nuclear division - mitosis
Usually followed by cytoplasmic division
Four stages:
Prophase
Metaphase
Anaphase
Telophase

18. Prophase Duplicated chromosomes begin to condense
New microtubules are assembled
One centriole pair is moved toward opposite pole of spindle
Nuclear envelope starts to break up

19. Metaphase Spindle forms
Spindle microtubules become attached to the two sister chromatids of each chromosome
All chromosomes are lined up at the spindle equator
Chromosomes are condensed

20. Anaphase Sister chromatids of each chromosome are pulled apart
Once separated, each chromatid is a chromosome

21. Telophase Chromosomes decondense
Two nuclear membranes form, one around each set of unduplicated chromosomes

22. Results of Mitosis Two daughter nuclei
Each with same chromosome number as parent cell
Chromosomes in unduplicated form

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

24. Animal Cell Division
Cleavage furrow

25. Plant cell Division
Cell Plate Formation

26. When Control Is Lost
Growth and reproduction depend on controls over cell division
Checkpoint proteins:
Growth factors invite transcription of genes that help the body grow
Other proteins inhibit cell cycle changes, such as after chromosomal DNA gets damaged
When all checkpoint mechanisms for a particular process fail, a cell loses control over its replication cycle
An example of this is cancer

27. Types of Cancers
Are abnormal masses of cells that lost controls over how they grow and divide
Benign – grow slowly and retain surface recognition proteins that keep them in a home tissue (noncancerous)
Malignant – grow and divide abnormally, disrupting surrounding tissues physically and metabolically (cancerous)

28. Cancer Research Described in Egyptian records 2625 BC
In Greek records ~440 BC
Greek for “Like a crayfish/crab”