1. Mitosis & Meiosis CHAPTER 11

2. CHROMOSOMES
Chromosome: DNA in a Eukaryotic cell that is tightly coiled and compacted in the cell nucleus
Histones:
Proteins in
Which DNA is
Tightly wrapped
Around that
Help maintain
The shape of
The chromosomes

3. Chromosome Structure:
Chromosome numbers:
Chromosomes are categorized as either sex chromosomes or autosomes
Sex chromosomes: chromosomes that determine the sex of an organism
Autosomes: all other chromosomes in an organism

4. Homologous chromosomes: one copy of each autosome from each parent
Homologous chromosomes: one copy of each autosome from each parent. The two copies of each autosome are called homologous chromosomes
Diploid: cells having 2 sets
Of chromosomes
Haploid: cells which contain
only one set of chromosomes

5. Karyotype: photomicrograph of the chromosomes in a cell

6. Cell division in prokaryotes: Binary fission

7. Mitosis:
If a cell wants to make a duplicate of itself, it first must copy its DNA (part of a chromosome).
The copies then must be separated & sorted into two sides of the cell.
The cell then splits in two. Part of each parent is carried to the two new cells.
Results in cells such as internal organs, skin, bones, blood, etc.

8. Mitosis Mitosis animations: http://www.youtube.com/watch?v=VlN7K1-9QB0
Beginning of second class

9. Interphase occurs just before Mitosis begins:
Cells spend most of the cell cycle in interphase
During g1 – offspring cells grow to mature size
During S phase- cells DNA is copied
During g2 phase- cell prepares for cell division (mitosis)

10. G0 phase
Cells can sometimes exit the cell cycle usually from the g1 phase and enter s state called g0
During g0, cells do not copy their DNA and do not prepare for cell division.
Many cells in the human body are in the g0 phase

11. Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Interphase
Animal cell
Plant cell
Photographs from:

12. 1st step in Mitosis: Prophase (preparation phase)
The DNA recoils, and the chromosomes condense; the nuclear membrane disappears, and the mitotic spindles begin to form.

13. Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Mitosis Prophase
Animal cell
Plant cell
Photographs from:

14. 2nd step in Mitosis: metaphase
The chromosomes line up the middle of the cell with the help of spindle fibers attached to the centromere of each replicated chromosome.

15. Mitosis Metaphase Animal cell Plant cell
Photographs from:

16. 3rd step in Mitosis: Anaphase (separation phase)
The chromosomes split in the middle and the sister chromatids are pulled by the spindle fibers to opposite poles of the cell.

17. Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Mitosis Anaphase
Plant cell
Animal cell
Photographs from:

18. 4th step in Mitosis: Telophase
spindle fibers dissasemble, and the chromosomes return to a less condensed chromatin state.
A nuclear envelope forms around each set of chromosomes and a nucleolus forms in each of the newly formed cells.

19. Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Mitosis Telophase
Animal cell
Plant cell
Photographs from:

20. After Mitosis: Cytokinesis
Beginning of cytokinesis in a plant:
a plate forms along the midline of the dividing cell
The actual splitting of
the daughter cells into
two separate cells is
called cytokinesis and
occurs differently in
both plant and animal
Cells.
Beginning of cytokinesis in an animal:
cell membrane pinches in at the middle of the dividing cell(this is called a cleavage furrow)

21. IPMATC REMEMBER! Interphase Prophase Metaphase Anaphase Telophase
Cytokinesis
IPMATC
A mnemonic to help remember the stages of mitosis.
Now do the mitosis flip books
End of second class
Julie Camp’s mitosis power point - 21

22. Meiosis:
As in mitosis, if a cell wants to make a duplicate of itself, it first must copy its DNA (part of a chromosome).
Results in reproductive cells (sperm, eggs, etc).
Part of each parent is carried to the four new cells.

24. Meiosis Interphase
The cell grows and copies its DNA, and the chromatin begins to condense into chromosomes.

25. -DNA coils tightly into chromosomes and spindle fibers appear
-In meiosis the homologous chromosomes pair with one another to form tetrads
- Portions of chromatids may break off and attach to adjacent chromatids, this process is called crossing over.
Meiosis Prophase I

26. Meiosis Metaphase I
- The tetrads line up randomly along the midline of the cell
-Spindle fibers attach to the centromeres of each homologous chromosome

27. Meiosis Anaphase I -The chromosomes move to opposite ends of the cell.
- The random separation of the homologous chromosomes is called independent assortment

28. Meiosis Telophase I & Cytokinesis
The cell begins to divide into two daughter cells. It is important to understand that each daughter cell can get any combination of maternal and paternal chromosomes.

29. Meiosis Prophase II
Spindle fibers form and begin moving chromosomes toward the middle of the cell

30. Meiosis Metaphase II
As in Meiosis I, the chromosomes line up on the spindle fibers at the midline of the cell.

31. Meiosis Anaphase II
The two cells each begin to divide. As in Meiosis I, the chromosomes move to opposite ends of each cell.

32. Telophase II & Cytokinesis
- a nuclear membrane forms around the chromosomes in each of the four new cells.
Cytokinesis II then occurs.
- each new cell contains half the original cells number of chromosomes