1.  Take out journals and pick up handout! Bell-Ringer: Chromosomes Meiosis vs. Mitosis notes Crossing Over activity

2. Scenario: Johnny misses class on Thursday. We learn something of importance that will be on the test next Tuesday. Day of the test, he walks up to Ms. M and says ‘I wasn’t here on Thursday when we learned some of this.’ What happens next? (besides my mind exploding) WHAT SHOULD HAVE HAPPENED?

3. Bell-Ringer: 11/30/15 HOW MANY CHROMOSOMES ARE FOUND IN EACH HUMAN BODY CELL?

4. Section 10.2 Summary – pages 263-273 In the body cells of animals and most plants, chromosomes occur in pairs. In each pair, you inherited one from your mom, the other from your dad. From Mom From Dad

5. Section 10.2 Summary – pages 263-273 The two chromosomes of a pair are called homologous chromosomes. Each pair of homologous chromosomes has genes for the same traits. Homologous Chromosomes

6. Section 10.2 Summary – pages 263-273 Each pair of homologous chromosomes has genes for the same traits. Homologous Chromosomes momdad -same size -same shape -same genes located in the same place

7. Section 10.2 Summary – pages 263-273 A cell with two of each kind of chromosome is called a diploid cell. Also called SOMATIC cells All of your body cells are diploid (2n). Diploid Cells

8. Section 10.2 Summary – pages 263-273 Body cells (diploid) are different from sex cells. Each person can only pass on ONE of their homologous chromosomes to their young. HUMANS = 46 CHROMOSOMES IN THEIR BODY CELLS Each parent passes 23 to their young, so that when the sperm and egg combine- it will equal 46 Chromosomes.

9. Section 10.2 Summary – pages 263-273 So, sex cells CANNOT be diploid. A cell containing only one of each kind of chromosome is called a haploid cell (n). Also called GAMETES Haploid Cells

10. Section 10.2 Summary – pages 263-273 Sexual Reproduction Zygote

11. Section 10.2 Summary – pages 263-273 Chromosome Numbers of Common Organisms Organism Body Cell, Diploid # Fruit fly 8 Garden pea14 Corn20 Tomato24 Leopard Frog 26 13 Apple34 Human46 Chimpanzee48 Dog78 Adder’s tongue fern 1260 Sex Cell, Haploid # 4 7 10 12 17 23 24 39 630 Diploid and Haploid Cells

12. In Humans, how many chromosomes would each of these cells have….. CHEEK CELL 46 SPERM CELL 23 EGG CELL 23 NERVE CELL 46

13. Since they have different amounts of chromosomes, they are made in different ways ● Body cells are made by the division process MITOSIS. ● Sex cells are made by the division process MEIOSIS.

14. Before a cell can divide by either method, it must first prepare for cell division. The cell cycle (or entire life cycle of the cell) consists of: INTERPHASE: The longest/busiest stage in a cell’s life 1. Chromosomes (DNA) replicates 2. Cell grows bigger NUCLEAR DIVISION: Mitosis or Meiosis CYTOKINESIS: When the cytoplasm divides and the cell completely separates.

15. Mitosis: cell division that makes BODY CELLS. It starts with a DIPLOID cell 46 Chromosomes Replicate 92 46 It ends with TWO IDENTICAL DIPLOID cells

16. Meiosis I Meiosis II The kind of cell division that produces sex cells (haploid) containing half the number of chromosomes as a body cell, is called meiosis.

18. Meiosis: cell division that makes SEX CELLS. It starts with a DIPLOID cell 46 Chromosomes Replicate 92 46 23 It ends with FOUR HAPLOID cells (NOT identical)

19. MALE MEIOSISFEMALE MEIOSIS Spermatocyte Diploid Oocyte Diploid Sperm (Haploid Gametes) Eggs / Ova (Haploid Gametes)

20. Crossing-Over During Meiosis: Homologous chromosomes actually break and exchange traits- in a process known as crossing over. Takes place during Prophase I

21. FROM MOM FROM DAD This chromosome inherited by mom could code for straight hair, brown hair, and green eyes… This chromosome inherited by dad could code for curly hair, black hair, and brown eyes… After crossing-over Now one chromosome passed on to offspring could have traits from both homologous… curly hair, brown hair, and green eyes…

22. Crossing over can occur at any location on a chromosome, and it can occur at several locations at the same time. This causes the traits found in each gamete varied. This is why siblings of the same parents can look so different from each other.

23. Section 10.2 Summary – pages 263-273 The failure of homologous chromosomes to separate properly during meiosis is called nondisjunction. This would occur when homologous chromosomes are suppose to separate from each other. Nondisjunction

24. Section 10.2 Summary – pages 263-273 These haploid cells are called sex cells- gametes. Male gametes are called sperm. Female gametes are called eggs. Meiosis They are created in the male sex gland, which are testes. They are created in the female sex gland, which are ovaries.

25. Section 10.2 Summary – pages 263-273 When a sperm fertilizes an egg, the resulting zygote once again has the diploid number of chromosomes. Meiosis Zygote = a fertilized egg

26. Section 25.1 Summary – pages 673 - 679 Cell division

27. Get your comp book 1. Put in your Meiosis Notes 2. Prepare a page for “Crossing Over/ Genetic Variation” In this activity, you will model Crossing over that occurs during Prophase I of Meiosis and discover how this small event causes genetic variation in siblings.

28. 1.Take your strip of paper This will end up being one homologous pair of chromosomes. The six bands will represent different genes What are genes?

29. 2.# The bands 1-6 starting at the top Write the # of the band on both sides

30. 3.Color the bands as follows: 1. Blue 2. Red 3. Purple 4. Green 5. Brown 6. Yellow 4.Label the Type of Gene at the bottom of each band… 1. Dimples 2. Hair Texture 3. Tongue Curl 4. Hitch Hiker Thumb 5. Cleft Chin 6. Anxiety

31. 5.Cut your strip in half long-ways These two strips represent Homologous chromosome pair #1

32. 6. For each chromosome, assign a characteristic that was passed down for each gene. For example: In the “Hair Texture” band you could write Straight, Curly, or Wavy Give only 1 characteristic per gene

33. Homologous Chromosome Pair #1 Pretend this homologous pair is in either a Spermatocyte or Oocyte… and it is time for Meiosis

34. During Meiosis Prophase I Homologous Chromosomes break and exchange genes (Crossing Over) 7. Cut away two genes on both chromosomes and exchange them

35. 8.Tape up your newly crossed-over chromosomes. This ‘mixes it up’ So your chromosomes should still have the same genes in the same order 1-6, BUT have a different mix of characteristics than before.

36. During Anaphase your chromosomes are parted from each other and are put in different sex cells. When one of these sex cells unites with another then the new baby will have a complete set of homologous chromosomes. 9. Find someone in class and trade ONE of your homologous chromosomes.

37. Pretend you and your classmate have created siblings (two children from the same parents) 10.Tape/glue your sibling’s homologous pair #1 in your comp book. -One chromosome should be yours -The other chromosome should be from the other parent. Answer the questions on the next slide about crossing over and genetic variation.

38. Answer these questions in your comp. book: 1.How does Crossing Over create genetic variation? 2.Specifically how were the genes/characteristics different in the siblings even though they came from the same parents? 3.Why is Crossing over important in Meiosis? 4.Are there any traits that your sibling could possibly pass down to the next generation that the other sibling could not? EXPLAIN. -Dimples are dominant over no dimples -Curly hair is dominant over wavy hair -Wavy hair is dominant over straight hair - Tongue curling is dominant over no tongue curling -Hitchhiker thumb is recessive to straight thumb -Cleft chin is dominant over no cleft chin -Having anxiety is dominant over not having anxiety