1. Cell Cycle and Mitosis a.k.a. Cell Reproduction
Biology is the only subject in
which multiplication is the same
thing as division

2. Introduction All organisms start with a single cell.
All new cells are produced from other, already existing cells.
Millions of cell divisions take place in our bodies every day to replace the cells that have died
Cell Type
Approximate Life Span
Skin Cells
2 weeks
Red Blood Cells
4 months
Liver Cells
days
Intestine-internal lining
4-5 days
Intestine-muscles and other tissue
16 years
Source: Spaulding et al., Cell 122:1.

3. Type of Cells it occurs in
3 Types of Cell Division
Type of Cell Division
Type of Cells it occurs in
Function
Binary Fission
Prokaryotes
Asexual Reproduction
Mitosis
Eukaryotes
Growth of Individual
Repair/Maintenance of Tissues
Meiosis
Sexual Reproduction

4. Binary fission Asexual reproduction of a Prokaryotic cell
Bacteria (Ex E. coli = every 20 minutes)
How many bacteria will result from 1 bacteria 7 hours (optimal conditions)? 1 million!

5. Binary Fission Begins with the duplication of the genetic material
A plasma membrane splits the cell in two, with each side containing a single copy of the DNA
The resulting two daughter cells replace the single parent cell and are genetically identical

6. Eukaryotes Use Mitosis to Generate Identical Daughter Cells
Multiphase process in which the cell divides from 1 parent cell to 2 identical daughter cells.
Occurs in all cells except reproductive cells
Mitosis is how asexual cell are replicated.
Meiosis is how sex cells are produced (we will look at this process later in the term)

7. The Cell Cycle Interphase is not part of mitosis!!
This is when the cell is doing its “everyday” jobs and getting ready for mitosis
Interphase is divided into 3 phases:
G1 = 1st Gap
cell doing its “everyday
job”
cell grows
S = DNA Synthesis
copies chromosomes
G2 = 2nd Gap
prepares for division
produces organelles, proteins, membranes
Length of G1 differs the most from cell type to cell type
S, G2 and mitosis take about 12 hours in human cells
In embryos and children go through the cell cycle faster

8. The Cell Cycle Many adult cells enter a non-dividing phase called G0
The G0 phase can last from a few days to the lifetime of the organism
Ex: liver cells stay in G0 for approximately a year, then reenter the cycle

9. Organization of Genetic Material
For equal division of the DNA to occur it has to be organized
In interphase each DNA double helix is packaged with special proteins to form long strands of chromatin
Chromatin is further compacted during mitosis to form
chromosomes
DNA Packaging
DNA during Interphase
DNA during Mitosis

10. Organization of Genetic Material
One Chromosome
DNA is replicated during S phase, resulting in two identical pieces of DNA, known as sister chromatids
Each human cell has twice the usual amount of DNA at the end of S phase and the start of mitosis
The identical sister chromatids are held together at a region called the centromere

11. The Karyotype Describes All the Chromosomes in a Nucleus
Every species has its own characteristic number of chromosomes
The display of all the chromosomes in a somatic (non-sexual) cell is called the karyotype
Each of us has two of each chromosome, one from mom and one from dad.
This pair of chromosomes, one from mom and one from dad, are similar but not identical
They are called homologous chromosomes

12. Karyotypes Before and After S-phase of Cell Cycle
Before S-Phase
After S-Phase

13. Karyotype of The Human Genome Let’s not get Chromosomes, Homologous Chromosomes, and Sister Chromatids Confused!!
Copied Homologous Chromosomes
Homologous Chromosomes
This is part of a karyotype looking at just chromosome 1
Sister Chromatids

14. Prophase Metaphase Anaphase Telophase Video
4 Stages of Mitosis:
Prophase Metaphase Anaphase Telophase Video

15. Prophase Beginning of mitosis DNA compacts into chromosomes
Centrosomes appear and begin to move to opposite ends of cell making the poles of the cell
The nuclear envelope breaks down
The mitotic spindle forms. It is made up of microtubules attached to each centrosome
What is a microtubule? Remember from cytoskeleton?
Centrosomes (centro- center, some- body)

16. Metaphase
Sister chromatids attach to the spindle fibers at the centromere through the kinetochore
The kinetochores are patches of proteins that attaches to the microtubules
Each centromere has two kinetochores that attach to the spindle fibers, one from each centrosome
This causes the chromosomes to line up on the metaphase plate

17. Anaphase
Sister Chromatids separate and begin to move to opposite ends of the cell
The centrosomes shorten the spindle fibers dividing the sister chromosomes and bringing them to opposite side of the cell
Each chromatid is now considered a new chromosome

18. Telophase Begins when the new chromosomes reach the centrosome
The spindle fibers break down
Two new nuclei form and the nuclear envelope forms around the chromosomes at each pole of the cell
Chromosomes appear as chromatin
After telophase cytokinesis occurs

19. Cytokinesis in Animal Cells
Not considered a phase in mitosis
Follows telophase
The cell membrane moves inward to create two daughter cells
Occurs at the metaphase plate

20. Cytokinesis in Plant Cells
Since plants have cell walls they also have to build this between daughter cells.
Vesicles containing cell wall components move to the metaphase plate where the cell wall forms

21. How can you remember the order????
Answer this question....Where would you like your cat or dog to pee?
On a PMAT of course

22. The Cell Cycle Is Highly Regulated
Cells divide in response to internal and external signals
In humans, cell cycle regulatory proteins are activated by external signals to divide, advancing the cell from G1 to S phase and initiating DNA replication
Cell cycle regulatory proteins can stop or pause the cell cycle if conditions are not favorable for cell division
What is this condition called?
What happens when the cell does not stop at a checkpoint?

23. Cancer 6 key mutations Turn on cell division Ignore checkpoints
Turn on promoter genes
Ignore checkpoints
Turn off suppressor genes
Avoid programed cell death
Turn off “suicide” genes
Unlimited divisions
Turn on chromosome maintenance genes
Promotes blood vessel growth
Turn on blood vessel genes
Cell attachment, anchor and density dependence genes
Turn off touch censor gene

24. Some people love mitosis a little too much!