1. Meiosis
Chapter 11.4

2. MITOSIS Review Purpose? Mitosis = division of nucleus
Ensures each daughter cell gets complete set of DNA
Each daughter has SAME DNA as mother cell

3. Mitosis Review (continued)
Steps of Mitosis?
Prophase
Chromosomes formed and become visible
Nuclear membrane breaks down

4. Mitosis Review (continued)
Steps of Mitosis?
Prophase
Metaphase
Chromosomes line up in center of cell

5. Mitosis Review (continued)
Steps of Mitosis?
Prophase
Metaphase
Anaphase
Centromere completes replication; chromsomes pulled to opposite poles of cell

6. Mitosis Review (continued)
Steps of Mitosis?
Prophase
Metaphase
Anaphase
Telophase
Spindle fibers breakdown
Chromosomes unwind
Nuclear membrane reappears

7. Chromosomes Different organisms have different number of chromosomes
Adder's tongue fern
1262
Alligator 32
Carrot 18
Cat
Chimpanzee 48
Corn 20
Dog 78
Earthworm 36
Fruit fly 8
Garden pea
Gorilla
Guppy 46
Gypsy moth 62
Horse 64
Human
Lettuce
Mosquito 6
Oak 24
Orangutan
Shrimp
254
Chromosomes
Different organisms have different number of chromosomes
Observations?

8. Chromosomes Observations?
Organism
Number of chromosomes
Adder's tongue fern
1262
Alligator 32
Carrot 18
Cat
Chimpanzee 48
Corn 20
Dog 78
Earthworm 36
Fruit fly 8
Garden pea
Gorilla
Guppy 46
Gypsy moth 62
Horse 64
Human
Lettuce
Mosquito 6
Oak 24
Orangutan
Shrimp
254
Chromosomes
Observations?
Number of chromosomes does not imply size or complexity
Some organisms have same number of chromosomes
All numbers are even
1 set from mom
1 set from dad
2 sets  even #

9. Karyotype Picture of chromosomes grouped in order in pairs Homologous
pairs = same
genes; same
banding pattern

10. Karyotype Which pair does not match? Male: XY Female: XX

11. Mitosis
All cells produced by mitosis have same number of chromosomes as parent cells

12. Meiosis Purpose? Create gametes (reproductive cells)
Reproductive cells have only 1 set of chromosomes (1n - haploid)
Meiosis must reduce the number of chromosomes
Somatic (body) cells have 2 sets of chromosomes (2n - diploid)
1 diploid cell (2n)  4 haploid cells (1n)

13. Human gametes 1n = 23 chromosomes sperm egg 1n = 23 chromosomes
combine at fertilization
zygote
2n = 46 chromosomes

14. Interphase
Cell grows, replicates DNA, prepares for cell division

15. Meiosis I Reduces the number of chromosomes in a cell Composed of
Prophase I
Metaphase I
Anaphase I
Telophase I

16. Prophase I DNA coils into chromosomes Nuclear membrane disappears
Homologous chromosomes pair up (tetrads) 2n
diploid
tetrad

17. Genetic Recombination
Crossing-over may occur in Prophase I
Portions of chromosomes may be exchanged between homologous chromosomes

18. Metaphase I
Tetrads line up randomly in cell 2n
diploid

19. Anaphase I One homologue of each pair pulled to pole
Homologue = 2 chromatids

20. Independent Assortment
Random separation of maternal & paternal chromosomes
2 chromosome pr  4 possible combos
3 chromosome pr  8 possible combos
23 chromosome pr  ? possible combos

21. Independent Assortment
Random separation of maternal & paternal chromosomes
2 chromosome pr  4 possible combos
3 chromosome pr  8 possible combos
23 chromosome pr  223 possible combos
(8,388,608)

22. Telophase I Chromosomes at opposite poles
Nuclear membrane may or may not appear
CYTOKINESIS occurs 1n
haploid 1n
haploid

23. Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II

24. Prophase II
Centrioles move to opposite poles
Spindle fibers form

25. Metaphase II Chromosomes line up in center of cell
Fibers attach to centromeres

26. Anaphase II
Chromatids separate and pulled to opposite poles

27. Telophase II Chromosomes unwind Nuclear membrane reappears Cytokinesis
Result in 4 haploid cells
Differ in DNA

28. Asexual Reproduction Result of MITOSIS
Offspring are genetically IDENTICAL to parent
Advantageous if parent are well-suited to stable environment

29. Sexual Reproduction Result of MEIOSIS and union of gametes
Offspring are genetically DIFFERENT from parent
Advantageous if parent are NOT well-suited and/or environment is unstable