1. Mitosis and Meiosis Asexual v. Sexual Reproduction
Cell dIVISION
Mitosis and Meiosis
Asexual v. Sexual Reproduction

2. Cell Division “process where 1 cell splits into 2”
Replaces somatic (body) cells in multicellular organisms
Allows for multicelullar growth
Allows for asexual reproduction in plants

3. Chromosome – rod shaped structure made up
DNA and protein
a. held together by centromere
- holds chromatids together until they
separate during division
b. only found during cell division

5. Chromosome Number
Human/animal chromosomes – sex chromosomes and autosomes
Humans have 46 chromosomes in somatic cells
Karyotype – used to examine an individual’s chromosomes

7. Haploid Diploid Reproductive cells (sperm and egg)
Somatic cells (body-all other cells)
½ the # of chromosomes (23)
Has ALL chromosomes (46)
half the DNA
Has ALL DNA
N = haploid
2N = diploid

8. Haploid/Diploid Problems
Haploid  Diploid = sex cell  body cell ( x by 2)
Diploid  Haploid = body cell  sex cell ( ÷ by 2)
Diploid  Diploid = body cell  body cell Haploid  Haploid = sex cell  sex cell

9. Practice Problems
Dogs have 42 chromosomes in their diploid cells. How many are in their haploid cells?
If there are 23 chromosomes in a sperm cell, how many would be in the skin cell?
If there are 46 chromosomes in a nerve cell, how many would be in a blood cell?
If there are 23 chromosomes in a sperm cell, how many would be in a human ovum (egg)

10. Cell Division in Prokaryotes
Binary Fision – two identical cells are produced from one cell
* division in bacteria

11. Cell Division in Eukaryotes
Mitosis
Meiosis
Asexual Reproduction
Sexual Reproduction
Division of diploid cells (somatic cells)
Division of haploid cells (reproductive cells)
Results in 2 identical daughter cells
Results in 4 haploid daughter cells
1 division
2 divisions

12. Cell Cycle “series of events leading to cell division”
Interphase – occurs before mitosis begins
- longest part of the cell cycle

13. Mitosis Asexual Reproduction
Diploid cells split into 2 identical diploid cells
Allows body cells to be replaced and cells to GROW

14. Phases of Mitosis 1. Prophase Chromatin coils to make chromosomes
2 pairs of centrioles move apart and spindle fibers appear
2 types of spindle fibers
a. kinetochore fibers
b. polar fibers

15. 2. Metaphase
Kinetochore fibers move chromosomes to the center (equator) of the cell

16. 3. Anaphase
Spindle fibers grab the centromeres of each chromosome and pull the chromatids apart
Chromatids now separate (now called daughter chromosomes) and are pulled to the opposite poles

17. 4. Telophase
Spindle fibers disassemble and chromosomes return to a less tightly coiled chromatin state
Nuclear envelope and membrane reappear
Cytokinesis – splitting of the cytoplasm
a. cleavage furrow
b. 2 cells are equal in size
c. each cell receives an identical copy of the original cell’s chromosomes

18. Cytokinesis “division of the cytoplasm”
*animal cell – creates 2 new cells
* Plant cell – forms cell plate

19. Meiosis “sexual reproduction”
Fusing of 2 haploid gametes to form 1 diploid zygote

20. Stages
2 divisions
a. Meiosis I

21. b. Meiosis II

22. Sources of Genetic Variation
Crossing – over
Fertilization
Independent Assortment