1. MITOSIS AND MEIOSIS
Cell Division

2. MITOSIS ASEXUAL division of a cell
Occurs in EUKARYOTIC cells (they HAVE a nucleus)
Makes a clone
A CLONE is a genetically identical copy

3. MITOSIS
Produces offspring with the full DIPLOID number of chromosomes.
Ex. In a fruit fly, there are 8 chromosomes, so our diploid number (2n) is 8. 2n 2n 2n

4. MITOSIS
“Offspring” (daughter cells) are genetically identical to the “parent” cell.
In humans, mitosis is used for growth and repair of body tissues.
Ex. If you have a cut, mitosis is what helps the cut to heal.

5. MITOSIS
Picture

6. STAGES OF MITOSIS INTERPHASE
This “stage” is where the cell spends most of it’s “life”.
The cell prepares for division by making an exact copy of each chromosome. (replication)

7. STAGES OF MITOSIS PROPHASE The chromosomes become visible.
The nuclear membrane begins to disappear.
The SPINDLE FIBERS form between CENTRIOLES.

8. STAGES OF MITOSIS METAPHASE
The chromosomes “line up” in the middle of the spindle.
Spindles attach to centromere

9. STAGES OF MITOSIS ANAPHASE The chromosomes begin to separate
When they separate, each piece becomes a CHROMATID.

10. STAGES OF MITOSIS TELOPHASE (in ANIMAL cells)
Two new cells begin to form by pinching in (cleavage) at the membrane.
CYTOKINESIS-the division of cytoplasm

11. STAGES OF MITOSIS TELOPHASE (in PLANT cells)
Instead of pinching in, a CELL PLATE forms between the two daughter cells.

12. 3 REASONS MITOSIS OCCURS
1. As the cells divide, the organism increases in size.
2. In humans, mitosis occurs to replace dead red blood cells (about every 120 days).
3. Asexual cellular reproduction
Ex. Amoeba

13. MITOSIS PICTURES

14. MITOSIS PICTURES

15. MEIOSIS Sexual reproduction (involves 2 parents)
Makes sex cells (gametes)
These gametes are
___________________(male)
___________________(female)
The gametes are made in the gonads.
The gonads are
_______________________(males)
_______________________(females)

16. MEIOSIS All meiosis occurs in the GONADS Purpose:
To reduce the chromosome number so when 2 gametes combine (fertilization), a zygote is formed.

17. MEIOSIS
Picture of GAMETOGENESIS

18. MEIOSIS Oogenesis Spermatogenesis Occurs in the _______________
Forms of 1 egg and 3 polar bodies
The egg has half the chromosome number as the parent cell. (haploid number)
Spermatogenesis
Produces 4 sperm cells
Each sperm has half the chromosome number of the parent cell. (haploid number)

19. MEIOSIS Chromosome numbers are reduced during meiosis. Examples:
If a body cell has 46 chromosomes, the gamete will have _______.
If a dog’s skin cell has 72 chromosomes, each sperm cell will have _______.
If a liver cell has 32 chromosomes, how many chromosomes does the egg cell have? _____
If an alligator has 14 chromosomes in its sperm, how many chromosomes are in his mates egg cell? ______
If the haploid number is 23, then the diploid number is _____.

20. MEIOSIS Recombination of chromosomes causes GENETIC VARIATION.
Picture of fertilization

21. MEIOSIS
Meiosis is called reduction-division of chromosomes because the chromosome number is reduced and replicated before the cell divides.
Diploid  Haploid
2N  N

22. MEIOSIS Steps of meiosis: Meiosis I and Meiosis II During Meiosis I-
Interphase
Chromosomes pair up to form homologous pairs.
Prophase
Spindle forms and nuclear membrane disappears
Metaphase
Homologous Pairs line up in the middle of the spindle
A TETRAD is formed (sister chromatids)
This is called SYNAPSIS
Genetic information is shared
Anaphase
Homologous Pairs are separated from one another
This is called DISJUNCTION
Telophase
Cytoplasm divides
Each cell has the monoploid (haploid) number of chromosomes

23. MEIOSIS Steps of meiosis: Meiosis I and Meiosis II During Meiosis II-
Prophase II
Spindle forms and nuclear membrane disappears
Metaphase II
Chromosomes line up in the middle of the spindle.
Anaphase II
Chromosomes are pulled apart by spindles.
Telophase II
Cytokinesis (cytoplasm divides) and four DAUGHTER CELLS are formed (in males).*
*In females, only ONE viable monoploid cell is produced.

25. MEIOISIS

26. MEIOSIS

27. MITOSIS AND MEIOSIS