1. Cell Growth and Division
Honors Biology
Chapter 10

2. Cell Growth Living things grow larger due to an increase in cells
Larger the cell, the more demands on the DNA and the more transport of water and nutrients across the membrane
The surface area to volume ratio must also be maintained.

3. Cell Growth
Before the cell gets too big in size, it must divide into 2 new daughter cells via a process known as cell division
In order to divide, the cell must make a copy of its DNA so each cell has a set of instructions of how the body functions
DNA Replication

4. Cell Division Occurs in 2 main stages 1. mitosis – division of nucleus
2. cytokinesis – division of cytoplasm
Considered to be asexual since the two daughter cells are genetically identical to the parent cell
Source of new cells as organism grows and develops

5. Chromosomes Made of DNA and proteins
Cells of every organism have a specific number of chromosomes
humans = carrot = fruit fly = 8
Chromosomes are only visible during cell division, these structures form to compact the DNA to make it easy to divide

6. Chromosome Structure
Each chromosome consists of 2 identical “sister” chromatids
When the cell divides, the sister chromatids separate from each other. One chromatid goes to each of the 2 new cells
Each pair of chromatids are attached by the centromere. The centromere is usually located near the middle of the chromatid
The human body contains 46 chromosomes and 46 centromeres, each of which contain 2 chromatids
Short arm
Long arm
One chromosome with 2 identical sister chromatids

7. Cell Cycle 1. M Phase: (mitosis phase) mitosis and cytokinesis
During the cell cycle, a cell grows, prepares for division, and divides to form 2 new identical daughter cells, each of which then begin the cycle again.
The cell cycle consists of 4 phases
1. M Phase: (mitosis phase) mitosis and cytokinesis
2. G1 Phase: (gap phase) growth and activity
3. S Phase: (synthesis phase) DNA replication
4, G2 Phase: (gap phase) growth and activity
G1, S and G2 all used to be group together and called interphase

8. Cell Cycle
G1 Phase
M Phase
S Phase
G2 Phase

9. Interphase Cell spends more time in interphase than M phase
1. G1 Phase – Most growing occurs. Cells increase in size and synthesize new proteins and organelles
2. S Phase – Chromosomes are replicated. Key proteins are synthesized
3. G2 Phase – Shortest of the three phases. Organelles and molecules required for division are produced. When the cell completes this phase it is ready to enter the M phase and begin the process of cell division

10. Mitosis
Involves the centrioles (cell organelles made of proteins and microtubules) of the cell
Occurs in four stages
1. prophase – chromosomes appear and nuclear envelope breaks down
2. metaphase – chromosomes line up across center of cell
3. anaphase - sister chromatids separate into separate cells
4. telophase – chromosomes gather at opposite ends of two cells and two new nuclear envelopes begin to form

12. Interphase
During Interphase the chromosomes are not visible. The cell grows and replicates its DNA and centrioles
Spindle forming
Centrioles
Chromatin
Centromere
Nuclear envelope
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

13. Prophase Longest phase of mitosis
Chromatin condenses and chromosomes become visible
The nuclear envelope begins to break down
Centrioles separate and take positions on opposite sides of the cell
The spindle, a microtubule structure that helps separate the chromosomes, begins to form

14. Prophase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

15. Metaphase Chromosomes line up across the center of the cell.
Microtubules connect the centromere of each chromosome to the two poles of the spindle

16. Metaphase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

17. Anaphase
The centromeres that join the sister chromatids of the chromosome split and allow the sister chromatids to separate and become individual chromosomes
The chromatids continue to move until they have separated into two groups near the poles of the spindle
Anaphase ends when the chromatids stop moving

18. Anaphase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

19. Telophase Final stage of mitosis
Chromosomes begin to loosen and into a tangle of dense material
Two new nuclear envelopes begin to reform around the two clusters of chromosomes
The spindle begins to break apart and a nucleolus becomes visible in each daughter nucleus
Mitosis is now complete, 2 nuclei are formed, but the cells are not yet separated

20. Telophase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

21. Cytokinesis Separation of cytoplasm within a single cell
Typically occurs at the same time as telophase
Cell membrane is drawn inward until the separation of the cytoplasm into two nearly equal parts
Each part contains its own nucleus and organelles
In plants, a cell plate forms midway between the divided nuclei and a cell wall begins to appear in the cell plate

22. Cytokinesis Interphase Prophase Cytokinesis Metaphase Telophase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

23. Mitosis and Cytokinesis Video Segment
..\..\bio CD\Chapter 10A.mpg

24. Did you know???? KNOWLEDGE IS POWER!!!!!!!!!!!
All of the DNA in an adult human body could fit inside one ice cube, but if unwound, stretched out and joined end to end, it could reach from the earth to the sun and back again approximately 400 more times. 
KNOWLEDGE IS POWER!!!!!!!!!!!

25. Homework Assignment
This will be due tomorrow, start it in class now because it is a long assignment!!!
Suppose you were small enough to hitch a ride on a chromosome located in an animal cell that goes through mitosis and cytokinesis. Describe what you would see happening during EACH phase of the process