1. Mitosis
Somatic Cell
diploid
2n=46

2. Genetic Traits GENEPROTEIN TRAIT
Only traits that are written in your DNA code can be passed on to offspring.

3. Each chromatid is exactly the same.
Review
Each chromatid is exactly the same.
Same genes.
Same alleles.
centromere
SISTER chromatids

4. MEIOSIS Cell division that produces GAMETES (sex cells).
Gametes are haploid (n): cells with half the chromosome # as body cells (2n).
2 Divisions occur: Meiosis I and Meiosis II.

5. Chromosomes and Genes
Homologous chromosomes – one from mom and one from dad.
Both have the same genes but each can have different alleles.
ALLELE

6. Basic Vocabulary
Diploid (2N): cell that has homologous pair of chromosomes.
EX: Somatic/Body cells. Mitosis reates these.
Haploid cell (N): cell that has one chromosome from a homologous pair.
EX: Gametes
2N=6
n=3

7. Vocabulary Con’t
Tetrad: structure that results when a homologous chromosome pair wrap around each other during Prophase I of Meiosis I
TETRAD

8. Vocabulary Con’t
ZYGOTE: Diploid cell formed from the fusion of gametes (SPERM + EGG) .
Fertilization: process where fusion of gametes occurs.

9. Interphase
Identical to interphase in mitosis-
CELL PREPARES
G1 S G2

10. Meiosis I
Prophase I
Similar to prophase in mitosis (visible chromosomes, nm disappears)
***** Tetrads can form and Crossing Over can occur. Only happens in this stage!

11. Crossing Over During PRO I
While in a tetrad, crossing over can occur. Crossing over is when pieces of chromosomes are exchanged.
LEADS to GENETIC VARIATION/RECOMBINATION.
Tetrad

12. Metaphase I
Meiosis: chromosome pairs line up next to each other.

13. Anaphase I Spindle fibers are used to separate the homologous pairs.
Chromosomes still remain as sister chromatids (X)

14. Telophase I/Cytokinesis I
The chromosomes do not go into chromatin
2 daughter cells formed with 1/2 the total number.
Notice the chromosomes
are still X shaped.
n= 2

15. Meiosis II There is no Interphase between Meiosis I and Meiosis II.
Division of sister chromatids/doubled chromosomes.
4 haploid cells will be produced.

16. Prophase II
Spindle fibers reform in each cell. Note there are two daughter cells.

17. Metaphase II
Chromosomes in the two cells align in the middle.

18. Anaphase II
Sister chromatids separate

19. Telophase II/Cytokinesis II
Nuclear membrane reforms, chromosomes become chromatin, cytoplasm divides.
4 daughter cells formed- each with half (haploid) the total chromosomes of the original cell

20. Meiosis Square Dance

22. Mitosis vs. Meiosis

23. Products of Meiosis Spermatogenesis Oogenesis
In the males, all four cells will become sperm
Oogenesis
In females, only 1 cell develops into an egg (oocyte)
The three small cells are called polar bodies form due to unequal cytokinesis.

24. Compare and Contrast Gametes Sperm Egg Male Made in Meiosis Haploid
Made in Testicles
Female
Made in Ovaries

25. Fertilization
Sperm
haploid
n=23
Egg
Zygote
diploid
2n=46