1. Phases of Cell Division
Interphase (stage between cell division)
Prophase
Metaphase
Anaphase
Telophase
By: Ms. Reis

2. Review Each body cell has 2 sets of 23 chromosomes
Therefore a normal human cell has 46 chromosomes

3. Cell Division Cells divide for several reasons:
To repair and heal tissues
To exchange materials efficiently with their environment. Food comes in and wastes go out.
To send messages to the nucleus efficiently.

4. Mitosis
Mitosis is a process of cell division producing two daughter cells from a single parent cell.
The daughter cells are identical to one another and to the original parent cell.
Note: Parent cell - the cell that divides
Daughter cell – the cells that result from cell division

5. Down Syndrome
Karyotype photograph of the entire set of chromosomes. 23 pairs for a total of 46
In Down Syndrome-trisomic for chromosome 21, carries an extra chromosome

6. Karyotype
A photograph showing the number, shapes and sizes of chromosomes in a cell.
All pairs of chromosomes are homologus (identical in size and shape) except the sex chromosomes (23rd pair)
One chromosome comes from the father (paternal) one chromosome comes from the mother (maternal

8. The Cell Cycle

9. Interphase The cell prepares for mitosis by growing rapidly
Chromosomes duplicate in the nucleus
Longest stage of the cell cycle

10. Chromatin
DNA molecules & proteins in a tangled fibrous mass during interphase. Chromatin is composed of 60% protein, 35 % DNA, and 5 % RNA.

11. Centromeres
The original chromosome and its duplicate are attached at the centromere.
Sister chromatids – the original chromosome and its duplicate while attached at the centromere.

12. Prophase Chromosomes shorten and thicken Nuclear membrane dissolves
Centrioles move to opposite poles of cell in animal cells
Formation of spindle fibers
The chromatin, diffuse in interphase, condenses into chromosomes. Each chromosome has duplicated and now consists of two sister chromatids.  

13. Metaphase
46 sister chromatids line up at the equatorial plate.

14. Anaphase
Spindle fibers pull sister chromatids (duplicated chromosomes) apart to the opposite end of the cell.
Centromeres divide.

15. Telophase Cell begins to pinch in two
New nuclear membrane starts to form
Cytokinesis -division of the cytoplasm and organelles between both daughter cells

16. Conclusion
Each new cell ends up with the same amount of genetic material as the original cell.
Both daughter cells are identical to the parent cells.

17. Cytokinesis
In animal cells the cell membrane pinches inward at the equator of the cell, producing a furrow.
In plant cells a cell plate is formed across the equator of the cell. Cellulose is added to the cell plate to form a new cell wall.

18. Discussion Question
How many chromosomes would you expect to find in each daughter cell after mitosis?
Predict what might happen to each daughter cell if all the chromosomes moved to only one side of the cell during anaphase.
Why is it necessary to duplicate the nuclear material?