1. AIM: What is the difference between the chromosome number in our body cells and gametes? DN: What are gametes? How many chromosomes are in the gametes of humans?

2. What is Sexual Reproduction? It involves the joining of two cells to begin the development of a new individual. These special cells are called: Sex Cells (Gametes)

3. What are the names of these sex cells? Sperm Cell (Male) Egg cell (Female) The joining of a sperm cell with an egg cell is called fertilization.

4. How many chromosomes do we have in our cells? 46 chromosomes 23 pairs of chromosomes Karyotype OR

5. Why do we have 2 of each chromosome? One from mom and one from dad Each pair of chromosomes are called: Homologous Chromosomes

6. Homologous Chromosomes: Have genes that code for the same trait, but may have different versions of that trait Eye Color Hair Color MomDad BG B R Gene Part of a chromosome that codes for a trait

7. Chromatids are exact copies of each other Used during cell division Homologous chromosomes A pair of chromosomes that contain genes for the same trait can have different versions of that trait One copy from each parent

8. How many chromosomes do the offspring have after mitosis? 46X Mitosis Same amount as the parent cell Humans = 46

9. Do our sex cells have 46 chromosomes? NO!!!

10. What would happen if our sex cells did have 46 chromosomes? 46 + 92 Egg Offspring Sperm The offspring would have 92 chromosomes

11. A: Sexual Reproduction B: Egg Cell/23 chromosomes C: Zygote/46 chromosomes 1.Egg- 23 chromosomes 2.Sperm- 23 chromosomes 3.Fertilization- Zygote formed with 46 chromosomes

12. Sexual Reproduction: 23 + 46 Sperm Egg Offspring A fertilized egg cell is called a Zygote Characteristics of Sexual Reproduction: 1) Is the creation of a new individual from parents.2 2) Offspring are not genetically to the parents.identical The zygote has 46 chromosomes

13. Sex Cells: - SPERM and EGG Sex cells should have 1/2 the normal number of chromosomes Sex Cells (Gametes)

14. Chromosome Number Diploid cells: (2n) normal number of chromosomes (Body Cells) Haploid cells: (n) ½ the normal number of chromosomes (Sex Cells)

15. Meiosis The process by which sex cells are produced with half the number of chromosomes.

16. Meiosis is 2 Cell Divisions 1 st Cell Division 2 nd Cell Division 1 Diploid cell 4 Haploid Cells

17. What is the end result of meiosis? 46X 23X Meiosis 4 cells with ½ the number of chromosomes

18. Where does meiosis occur? Gonads – Ovaries and Testis

19. Why is meiosis important? Maintains the number of chromosomes from generation to generation Provides genetic variation.

20. Crossing over – Prophase I Synapsis – homologous chromosomes pair up Crossing over – chromosomes overlap and exchange of genes.

22. Gametogenesis Production of gametes (sperm & egg) By meiotic cell division Gameto = gametes Genesis = creation

23. Oogenesis Creation of an ovum or egg cell by meiotic cell division in the ovary.

24. How many eggs are produced? There is an unequal sharing of cytoplasm 1 egg & 3 non functional polar bodies

25. Egg vs. Polar Bodies The egg is very large, has most of the cytoplasm, which will provide nutrients for the offspring.

26. Spermatogenesis Creation of sperm cells by meiotic cell division in the testes.

27. How many sperm are produced by spermatogenesis? 4 equal sized sperms with flagella for swimming.

28. Spermatogenesis vs. Oogenesis

29. Practice Problems: