1. Standard VI- Mitosis and Meiosis
Biology AHSGE
Standard VI- Mitosis and Meiosis

2. Biology AHSGE
CONTENT STANDARD 6. Describe the roles of mitotic and meiotic divisions during reproduction, growth, and repair of cells.
ELIGIBLE CONTENT
A. Demonstrate an understanding of how meiosis leads to variation.
B. Describe the role of meiosis in producing variation.
C. Describe the role of meiosis in reproduction.
D. Describe the role of mitosis in cell repair.
E. Describe the role of mitosis in growth.
F. Describe the role of both mitosis and meiosis.

3. The Cell Cycle
When a eukaryotic cell reaches its size limit, it divides.
Cell Cycle- Reproduction by a cycle of growing and dividing.
Three phases:
Interphase- Cell growth, maturity, DNA duplication, and prep for division
Chromatin (relaxed form of DNA) strands make copies of themselves
Mitosis- Nuclear material divides and moves to opposite sides of the cell
Cytokinesis- Cytoplasm divides, and two identical daughter cells form

4. The Cell Cycle

5. The Cell Cycle and Mitosis
Purposes:
Increase the number of cells as a young organism grows into the adult form
Replace damaged cells
Regulation: Controlled by cyclins (proteins) binding to cyclin-dependent kinases (CDKs- enzymes)
Cancer- Uncontrolled division and growth of cells
Carcinogen- Known to cause cancer
Apoptosis- Programmed cell death
Stem cells- Unspecialized cells that can develop into specialized cells
Embryonic stem cells- First cells from a fertilized egg
Adult stem cells- Found in various tissues; may be used to maintain and repair those tissues

6. Mitosis- Prophase
Chromatin strands tighten (condense) into chromosomes
Sister chromatids- Identical halfs of a chromosome
Centromere- Center of attachment
Nucleolus disappears
Spindle Fibers appear and attach to opposite sides of centromeres and centrioles
Responsible for moving and arranging chromosomes
Centrioles move to the poles
Spindle apparatus- Spindle fibers, centrioles and aster fibers (star-like microtubules of centriole)
Nuclear envelope disappears

7. Mitosis- Metaphase
Sister chromatids are pulled by motor proteins along the spindle apparatus toward the center of the cell
Chromosomes line up in the middle, or equator, of the cell

8. Mitosis- Anaphase
Microtubules of spindle apparatus shorten, pulling the chromosomes in half
With the help of motor proteins, chromatid strands are pulled to opposite sides of the cell

9. Mitosis- Telophase
Chromatid strands arrive at ends of cell and decondense
Two new nuclear membranes form around chromatin
Nucleoli reappear
Spindle apparatus disassembles

10. Cytokinesis
Cytoplasm divides resulting in two cells with identical nuclei
In plants, a cell plate forms and new cell wall forms on each side
Binary fission- In prokaryotes, DNA is duplicated and copies attach to cell membrane. Membrane grows and pulls apart DNA molecules. Cell completes fission, resulting in two identical cells.

11. Standard VI- Mitosis and Meiosis
AHSGE Biology
Standard VI- Mitosis and Meiosis

12. Chromosomes Traits- Characteristics passed to offspring from parents
Instructions found on chromosomes
Genes- segments of DNA found on each chromosome; approx per chromosome
Homologous Chromosomes- Pairs of chromosomes; one from each parent
Humans- 23 pairs; 23 from each parent
46 total chromosomes

13. Haploid Vs. Diploid
Gametes- Sex cells with half the number of chromosomes
Created to maintain the chromosome number from generation to generation
Represented by symbol n
Haploid- A cell with n number of chromosomes
Human gametes- n = 23
Fertilization- Fusion of gametes
Results in 2n zygote (fertilized egg cell)
Diploid- A cell with 2n number of chromosomes
Human somatic (regular body cells) cells- 2n = 46

14. Meiosis Forms gametes with genetic variation
Spermatogenesis- process of producing sperm with half the number of chromosomes
Undifferentiated- no flagellum
Oogenesis- the creation of an ovum (egg cell)
three polar bodies all die (incomplete egg cells)
Reduction division- Reduces the number of chromosomes in half
2n ⃗ n (Diploid to haploid)
Occurs in reproductive structures of sexual organisms
Involves two divisions: Meiosis I and Meiosis II

15. Meiosis I Cell undergoes Interphase Prophase I
Homologous chromosomes condense and pair up (synapsis)
Crossing over- segments or genes are exchanged during synapsis
Centrioles move to opposite poles and spindle fibers attach to centromeres

16. Crossing Over

17. Meiosis I
Metaphase I- Homologous chromosomes (pairs) line up at the equator
Anaphase I- Homologous chromosomes separate and move towards opposite poles (disjunction)
Reduces chromosome number from 2n to n
Independent Assortment- random segregation and assortment of chromosomes during gametogenesis (production of gametes); aids in increasing genetic diversity

18. Meiosis I Telophase I- Individual chromosomes arrive at opposite poles
Cytokinesis occurs
Nuclear membrane and nucleoli reappear
Two new cells formed, each with new genetic variation

19. Meiosis II Prophase II- Occurring in two cells Chromosomes condense
Nucleolus disappears
Spindle Fibers appear and attach to opposite sides of centromeres and centrioles
Centrioles move to the poles
Nuclear envelope disappears

20. Meiosis II
Metaphase II- Sister chromatids are pulled by motor proteins along the spindle apparatus to line up at the equator

21. Meiosis II
Anaphase II- Microtubules of spindle apparatus shorten, pulling the chromosomes in half and to opposite sides of the cell

22. Meiosis II Telophase II
Chromatid strands arrive at ends of cell and decondense
Two new nuclear membranes form around chromatin
Nucleoli reappear
Spindle apparatus disassembles
Cytokinesis occurs
Four unique, haploid (n) gametes result

23. Mitosis
Meiosis
One division
Two divisions: Meiosis I and II
DNA replication in Interphase
DNA replication once in Meiosis I
Synapsis doesn’t occur
Synapsis occurs
Two identical, diploid cells
Four different, haploid cells
Somatic cells
Reproductive cells
Growth and repair
Gametes & genetic variation