1. Meiosis
Organisms that reproduce sexually have specialized cells called gametes (sex cells)
Gametes are the result of a type of cell division called meiosis

2. Diploid and haploid
Almost all human cells are diploid or containing two homologous sets of chromosomes
2n = 46
Eggs and sperm cells (gametes) are haploid or containing a single set of chromosomes
n = 23

3. ORGANISM (Genus species) NUMBER OF CHROMOSOMES
Homo sapiens (human)______________________________46
Mus musculus (house mouse)_________________________40
Drosophila melanogaster (fruit fly)_____________________8
Caenorhabditis elegans (microscopic roundworm)_________12
Saccharomyces cerevisiae (budding yeast) ______________32
Arabidopsis thaliana (plant in the mustard family) ________10
Xenopus laevis (South African clawed frog)______________36
Canis familiaris (domestic dog)________________________78
Gallus gallus (chicken) ______________________________28
Zea mays (corn or maize)____________________________20
Muntiacus reevesi (the Chinese muntjac, a deer) _________23
Muntiacus muntjac (its native american cousin) __________6
Myrmecia pilosula (an ant) ___________________________2
Parascaris equorum var. univalens (parasitic roundworm)___2
Cambarus clarkii (a crayfish)__________________________200
Equisetum arvense (field horsetail, a plant)______________216

4. Horsetail

5. HUMAN KARYOTYPE
A display of all the 46
chromosomes of an
Individual.

6. 9.5 page 2

7. Remember Mitosis?

8. MITOSIS

11. Meiosis

12. haploid egg and sperm
diploid zygote
In the human life cycle a haploid egg and sperm fuse and form a diploid zygote. Mitosis produces an embryo with numerous cells that continue to multiply and develop.

13. 2 diploid daughter cells
MEIOSIS
MITOSIS
Original diploid cell 2n 2n 2n
2 diploid daughter cells

14. Genetic variation is a result of two processes that occurs during meiosis:
Independent assortment of chromosomes, and
Crossing over
NOTE: Mutations (random changes in gene sequences) are a cuse of genetic variation.

15. During metaphase I, the independent assortment of chromosomes that end up in the resulting cells occurs randomly

16. Crossing over: exchange of genetic material between homologous chromosomes during prophase I of meiosis

17. Genetic recombination: new combination of genetic information in a gamete as a result of crossing over during prophase I of meiosis

19. MITOSIS MEIOSIS TYPE OF CELL (that undergoes this division)
(pages 195, 200, & 201)
MITOSIS
MEIOSIS
TYPE OF CELL (that undergoes this division)
# OF CELL DIVISIONS
Starts/ends as diploid or haploid cell
# OF DAUGHTER CELLS
# OF CHROMOSOMES AFTER DIVISION
EXCHANGE OF DNA (Y/N)
UNIQUE OR IDENTICAL CELL AFTER DIVISION

20. Development of egg and sperm