1. What are Gametes?

2. Check Point 1. What is a gamete? –A sex cell 2. How many chromosomes does it have? –23

3. I. Human body cells have 46 chromosomes A. The cells in your body are “specialized”, which means that certain cells are specially formed to do certain jobs. B. They may look different, but all human cells (nerve, blood, skin, etc) have 46 chromosomes.

4. Common name SpeciesChromosome number HumanHomo sapiens46 Rhesus Monkey Macacca mulatta42 DogCanis familiaris78 CatFelis domesticus38 MouseMus musculus40 Leopard FrogRana pipiens26 Fruit FlyDrosophila melanogaster 8 CornZea mays20

5. C.Chromosomes are found in pairs in human cells. These pairs are roughly the same shape, and they code for the same genes. 46 human chromosomes= 23 pairs

6. Check point How many chromosomes does each human cell have? 46

7. D.Therefore a human body cell has 23 homologous pairs of chromosomes.

8. II. Fertilization A.Fertilization is when a sperm cell joins with an egg cell. B.When this happens, a zygote (or fertilized egg) is produced. += ZYGOTE

9. Check point 1. What does fertilization produce? –zygote 2. How many chromosomes does it have? –46 3. What does meiosis produce? –gamete 4. How many chromosomes does that have? –23

10. C.Through a series of mitotic cell divisions, the zygote becomes a baby. mitosis ZYGOTE

11. Check point What does mitosis produce? –2 identical daughter cells

12. If every cell in the human body had 46 chromosomes – what would be the result if a sperm fertilized an egg? + = ZYGOTE mitosis 46 92

13. But humans have 46 chromosomes, so this cannot be true! + = ZYGOTE mitosis ? ? 46

14. D. Egg and sperm cells each have 23 chromosomes. This is the only way that they can fuse together to produce a human with 46 chromosomes. + = ZYGOTE mitosis 23 46

15. Check point How much of your DNA comes from each parent? Half

16. III. Gametes A.Egg and sperm cells are called gametes. B.Human body cells have 46 chromosomes. Egg and sperm cells have 23 chromosomes. C.46 is the diploid (2n) chromosome number for humans.

17. D.23 is the haploid (n) chromosome number for humans. Diploid person 46 chromosomes in each cell Haploid gametes 23 chromosomes in each cell n2n

18. IV. Life cycle of a human Z

19. Z MeiosisFertilization

20. Summary How many chromosomes do humans have? Where do these chromosomes come from? What is fertilization? What are gametes? Which part of the human life cycle is haploid? Which part is diploid? What does this mean?