"Biology is the only science in which multiplication means the same thing as division."

1. MEIOSIS "Biology is the only science in which multiplication means the same thing as division."

2. Meiosis • Comes from a Greek word that means: • “to make smaller” • also known as reduction division

3. Learning Goals:(for this section) • 1. Explain the difference between Mitosis and Meiosis

4. 2. Descibe how chromosomes determine sex.

5. 3.Explain why sex-linked disorders occur in one sex more than in the other.

6. Interpret a pedigree

7. Section vocab:

9. MCAS: Unit: HeredityE.U: Organisms reproduce either asexually or sexually. Sexual reproduction leads to a genetic variation.

10. Why does a pug….

11. Look so different from a… Doberman pincher?

12. Answer? Meiosis (And Selective Breeding)

14. Two Kinds of Reproduction • Asexual • One parent cell is needed to reproduce ex. Mitosis • Sexual • Two parent cells join together to form a new individual. • Requires meiosis !

15. There are two categories of cells in the human body: • 1.)Somatic cells (body cells) • These have 46 chromosomes in every nucleus of every cell. • These cells are produced through mitosis, a form of asexualreproduction-(review on next slide)

16. Review of mitosis:

17. 2.)Sex cells: • Eggs in females • Sperm in males • All contain only 23 chromosomes (1/2 that of body cells) These cells are produced by meiosis. (this process is needed for sexual reproduction)

18. When sex cells are made, chromosomes are copied once and then the nucleus dividesTWICE.

19. How does MEIOSIS happen? • One cell produces 4 cells with ½ the DNA • Meiosis: An Interactive Animation

20. Each of the new cells has HALF the number of chromosomes found in the original cell !

21. MEIOSIS PROVIDES___ IN A SPECIES. ? Variation !

22. 8 Steps in Meiosis Steps of Meiosis

23. MEIOSIS PRODUCES: • Sex cells: • Eggs • Sperm Tap me (best meiosis video ever)

24. Comparison of Mitosis and Meiosis both mitosis meiosis

25. SEX CHROMOSOMES: • Contain genes that determine an offspring’s sex • HUMAN FEMALES HAVE: Xand X • HUMAN MALES HAVE: X and Y

26. What are the chances of getting a boy or a girl? BRAIN POP

27. Karyotype:a picture of human chromosomes all lined up:

29. Sex-linked Disorders • The Y chromosome is small and does not carry all of the genes of an X chromosome

30. Females have 2 “X” chromosomes recessive

31. Females therefore carry a copy of each gene found on the X chromosome. • (this allows the recessive disorder gene to be masked) • Males have only one copy of each gene on their X chromosome • If they inherit the disorder on this chromosome, they will have the disorder • Examples are Color Blindedness,Hemophilia (bleeder’s disease), and Cystic Fibrosis

32. Colorblind tests

33. Hemophilia

34. Cystic Fibrosis Cystic fibrosis is an inherited chronic disease that affects the lungs and digestive system of about 30,000 children and adults in the United States (70,000 worldwide). A defective gene and its protein product cause the body to produce unusually thick, sticky mucus.

35. To tell a sex linked disorder in a pedigree… • Females are carriers of the trait • Males have the trait

36. Pedigree: • A diagram that shows the occurrence of a trait in several generations of a family.

37. Pedigree Rules • Squares represent males • Circles represent females • Vertical lines connect children to parents • Solid circle or square indicates that the person has a certain trait • A half-filled square or circle indicates the person is a carrier of the trait.

38. Pedigree

40. Faster race horses Bigger petals Newer colors Selective Breeding • Organisms with desirable characteristics are mated High egg layers Bigger,fatter, tastier White colored pumpkins

41. Ex: People have been breeding dogs for desired traits for thousands of years.

42. Example: • Mate a poodle and a golden retriever • Hair, not fur • Smart • Fur that sheds, • Retrieves • Loyal

43. Golden Doodle • Hair, not fur • Smart • Retrieves • Loyal