1. Meiosis!
Chapter 10.2

2. Meiosis: cell division to produce GAMETES!!
Sperm= male gamete (haploid)
Egg= female gamete (haploid)

3. Vocabulary! (needed before we can discuss meiosis)
Gene—section of DNA that codes for a trait
Allele– a version of a gene. Ex?
Chromatin– uncoiled, stringy DNA
Chromosome– piece of packaged DNA that is easier to move around.

4. Chromosome
CENTROMERE – the place where two sister chromatids are attached.

5. Vocabulary
Homologous Chromosomes— paired chromosomes that have genes for the same traits (in the same order)
One homologous chromosome of each pair comes from mom
One homologous chromosome of each pair comes from dad

6. Vocabulary
Haploid—gametes which have half the number of chromosomes - are labeled 1N (1N= 1 set of chromosomes).
Diploid—A full set of chromosomes from each parent (2N = 2 sets of chromosomes)
*Ploid= # of SETS of chromosomes

7. Practice with Diploid and Haploid
Chromosome Numbers of Common Organisms
Organism
Diploid Body Cell (2N)
Haploid Gamete (1N)
Fruit Fly 8
Garden Pea 14
Corn 20
Tomato 12
Leopard Frog 13
Apple 17
Human 46
Chimp 48
Dog 39
Fern
630
Organism
Body Cell (2n)
Gamete (n)
Fruit fly 8 4
Garden pea 14 7
Corn 20 10
Tomato 24 12
Leopard Frog 26 13
Apple 34 17
Human 46 23
Chimpanzee 48 24
Dog 78 39
Adder’s tongue fern
1260
630

8. Vocabulary
Sexual reproduction: When 2 haploid cells unite (fertilization)
Zygote= fertilized egg =1st cell of offspring (Diploid)

9. Before Meiosis INTERPHASE Normal cell life and metabolism
DNA is uncoiled chromatin.
DNA is replicated (copied)!
Why?

10. Starts with one diploid cell
MEIOSIS
Meiosis: cell division which produces 4 haploid gametes
Starts with one diploid cell
Ends with four haploid cells

11. Meiosis has two divisions
Meiosis I
4 phases
Meiosis II
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12. Meiosis I Prophase I Nuclear envelope/nucleolus disappear
Spindle apparatus forms.
Chromosomes become visible (chromatin condenses)
Homologous Chromosomes Pair up.
Tetrad
Crossing Over (Recombination) occurs
the exchange of genetic material between homologous chromosomes.

13. Metaphase I Tetrads line up on the metaphase plate
Alignment is random (Independent Assortment of Chromosomes)

14. Anaphase I
Homologous Chromosomes separate and move to opposite poles

15. Telophase I Cytokinesis The cytoplasm divides
Nuclear envelope re-forms
Spindle breaks down
Cytokinesis
The cytoplasm divides
Two new HAPLOID cells are created

16. Meiosis II Prophase II Nuclear envelope disappears
Spindle apparatus forms and attaches to chromosomes

17. Metaphase II
Chromosomes line up down metaphase plate (middle)

18. Anaphase II
Sister chromatids separate and move toward opposite poles

19. Four haploid gametes have been formed!!
Telophase II
Nuclei reform
Spindle breaks down
Cytokinesis
Cytoplasm divides
Four haploid gametes have been formed!!
C:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 10 BDOL IC

20. Meiosis produces Diversity!
How?
Crossing over
Independent Assortment
Details…

21. Crossing-over
Crossing over is the exchange of genetic material between homologous chromosomes.
This increases the genetic variation in the gametes.

22. Independent Assortment
The random distribution of chromosomes during meiosis.
This independent assortment produces millions of possible gametes
See picture…

24. Good Meiosis Video:

25. Nondisjunction
Nondisjunction—the failure of homologous chromosomes or sister chromatids to separate during Meiosis
Trisomy— an extra chromosome
Ex. Down syndrome (trisomy 21)
Monosomy- having one less chromosome
Polyploidy= abnormal # of sets of chromosomes

26. Analyze the Karyotypes

27. Mitosis versus Meiosis
1. Mitosis produces diploid cells
2. Meiosis produces haploid cells
3. Mitosis produces two cells with the same genetic (DNA) material
4. Meiosis produces four cells with different genetic material.