How to Use This Presentation

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2. Resources Bellringers Chapter Presentation Transparencies Standardized Test Prep Visual Concepts Image and Math Focus Bank

3. Chapter C3 Heredity Table of Contents Section 1 Mendel and His Peas Section 2 Traits and Inheritance Section 3 Meiosis

4. Chapter C3 Section1 Mendel and His Peas Bellringer • You have probably noticed that different people have different characteristics, such as eye color, hair color, and ear lobes that do or do not attach directly to their head. Where do you think people get these different traits? • Record your answers in your science journal.

5. Chapter C3 Section1 Mendel and His Peas Objectives • Explain the relationship between traits and heredity. • Describe the experiments of Gregor Mendel. • Explain the difference between dominant and recessive traits.

6. Chapter C3 Section1 Mendel and His Peas Who Was Gregor Mendel? • Gregor Mendelwas born in 1822 in Heinzendorf, Austria. • At age 21, Mendel entered a monastery. He performed many scientific experiments in the monastery garden. • Mendel discovered the principles of heredity, the passing of traits from parents to offspring.

7. Chapter C3 Section1 Mendel and His Peas Unraveling the Mystery • Mendel used garden pea plants for his experiments. • Self-Pollinating Peashave both male and female reproductive structures. So, pollen from one flower can fertilize the ovule of the same flower. • When a true-breeding plant self pollinates, all of the offspring will have the same trait as the parent.

8. Chapter C3 Section1 Mendel and His Peas Unraveling the Mystery, continued • Pea plants can also cross-pollinate. Pollen from one plant fertilizes the ovule of a flower on a different plant. • The image below shows cross-pollination and self-pollination.

9. Chapter C3 Section1 Mendel and His Peas Unraveling the Mystery, continued • CharacteristicsMendel studied only one pea characteristic at a time. A characteristicis a feature that has different forms in a population. • Different forms of a characteristic are called traits.

10. Chapter C3 Section1 Mendel and His Peas Unraveling the Mystery, continued • Mix and MatchMendel was careful to use plants that were true breeding for each of the traits he was studying. By doing so, he would know what to expect if his plants were to self-pollinate.

11. Chapter C3 Section1 Mendel and His Peas Mendel’s First Experiments • Mendel crossed pea plants to study seven different characteristics. • Mendel got similar results for each cross. One trait was always present in the first generation, and the other trait seemed to disappear. • Mendel called the trait that appeared the dominant trait. The trait that seemed to fade into the background was called the recessive trait.

12. Chapter C3 Section1 Mendel and His Peas Mendel’s Second Experiments • To find out more about recessive traits, Mendel allowed the first-generation plants to self-pollinate. • In each case some of the second-generation plants had the recessive trait.

13. Chapter C3 Section1 Mendel and His Peas Mendel’s Second Experiments, continued • Ratios in Mendel’s Experiments The recessive trait did not show up as often as the dominant trait. • Mendel decided to figure out the ratio of dominant traits to recessive traits.

14. Chapter C3 Section1 Mendel and His Peas Mendel’s Second Experiments, continued In all cases the ratio was about 3:1 dominant : recessive.

15. Chapter C3 Section1 Mendel and His Peas Mendel’s Second Experiments, continued • Gregor Mendel – GoneBut Not Forgotten Mendel realized that his results could be explained only if each plant had two sets of instructions for each characteristic. • Mendel’s work opened the door to modern genetics.

16. Chapter C3 Section2 Traits and Inheritance Bellringer • If you flip a coin, what are the chances that it will land on heads? tails? Suppose that you flipped the coin and got heads. What are the chances that you will get heads again? • Record your answers in your science journal.

17. Chapter C3 Section2 Traits and Inheritance Objectives • Explain how genes and alleles are related to genotype and phenotype. • Use the information in a Punnett square. • Explain how probability can be used to predict possible genotypes in offspring. • Describe three exceptions to Mendel’s observations.

18. Chapter C3 Section2 Traits and Inheritance A Great Idea • Mendel knew that there must be two sets of instructions for each characteristic. • The instructions for an inherited trait are called genes. • The different forms (often dominant and recessive) of a gene are alleles. • Phenotype An organism’s appearance is known as its phenotype.Genes affect the phenotype.

19. Chapter C3 Section2 Traits and Inheritance A Great Idea, continued • Genotype The combination of inherited alleles together form an organism’s genotype. • Punnett Squares are used to organize all the possible genotype combinations of offspring from particular parents.

20. Chapter C3 Section2 Traits and Inheritance

21. Chapter C3 Section2 Traits and Inheritance What Are the Chances? • Probability is the mathematical chance that something will happen. • Probability is most often written as a fraction of percentage.

22. Chapter C3 Section2 Traits and Inheritance Calculating Probability

23. Chapter C3 Section2 Traits and Inheritance What Are the Chances?, continued • Genotype ProbabilityTo have white flowers, a pea plant must receive a p allele from each parent. Each offspring of a Pp Pp cross has a 50% chance of receiving either allele from either parent. So, the probability of inheriting two p alleles is 1/2  1/2, which equals 1/4, or 25%.

24. Chapter C3 Section2 Traits and Inheritance More About Traits • Incomplete Dominance Researchers have found that sometimes one trait is not completely dominant over another. • One Gene, Many Traits Sometimes one gene influences more than one trait. • Many Genes, One Trait Some traits, such as the color of your skin, hair, and eyes, are the result of several genes acting together.

25. Chapter C3 Section2 Traits and Inheritance More About Traits, continued • The Importance of EnvironmentGenes aren’t the only influences on traits. A combination of things determine an individual’s characteristics. • Your environment also influences how you grow. • Lifestyle choices can also affect a person’s traits.

26. Chapter C3 Section3 Meiosis Bellringer • Write a sentence to describe each of the following terms: heredity, genotype, and phenotype. Note how genotype and phenotype are related, and how they are different. Is heredity necessarily a factor in both genotype and phenotype? Why or why not? • Record your answers in your science journal.

27. Chapter C3 Section3 Meiosis Objectives • Explain the difference between mitosis and meiosis. • Describe how chromosomes determine sex. • Explain why sex-linked disorders occur in one sex more often than in the other. • Interpret a pedigree.

28. Chapter C3 Section3 Meiosis Asexual Reproduction • In asexual reproduction, only one parent cell is needed. The structures inside the cell are copied, and then the parent cell divides, making two exact copies. • This type of cell reproduction is called mitosis. Most of the cells in your body and most single-celled organisms reproduce this way.

29. Chapter C3 Section3 Meiosis Mitosis

30. Chapter C3 Section3 Meiosis Sexual Reproduction • In sexual reproduction, two parent cells (sex cells) join together to form offspring that are different from both parents. • Chromosomes that carry the same sets of genes are called homologous chromosomes. • Each sex cell has only one of the chromosomes from the homologous pair.

31. Chapter C3 Section3 Meiosis Sexual Reproduction, continued • MeiosisSex cells are made during meiosis. • Meiosis is a copying process that produces cells with half the usual number of chromosomes.

32. Chapter C3 Section3 Meiosis

33. Chapter C3 Section3 Meiosis

34. Chapter C3 Section3 Meiosis The Steps of Meiosis • During meiosis, chromosomes are copied once, and then the nucleus divides twice. • The resulting sex cells (sperm and eggs) have half the number of chromosomes of a normal body cell.

35. Chapter C3 Section3 Meiosis Meiosis and Mendel • The steps of meiosis explain Mendel’s results. The following slide shows what happens to a pair of homologous chromosomes during meiosis and fertilization.

36. Chapter C3 Section3 Meiosis

37. Chapter C3 Section3 Meiosis Meiosis and Mendel, continued • Sex Chromosomescarry genes that determine sex. • Human females have two X chromosomes. • Human males have one X chromosome and one Y chromosome.

38. Sex Linked Disorders • Some disorders are linked to the X and/or Y chromosomes • Usually recessive • Red/Green colorblindness is linked to the X chromosome (Xc)

39. Genotype = Phenotype XX = Not Colorblind Female XY = Not Colorblind Male XXc = Colorblind Carrier Female XcY = Colorblind Male XcXc = Colorblind Female

40. Red / Green Colorblindness

41. Sex Linked Disorders • Can be traced thru a family using a pedigree chart

42. Chapter C3 Heredity Concept Map Use the terms below to complete the concept map on the next slide.

43. Chapter C3 Heredity

44. Chapter C3 Heredity

45. End of Chapter C3 Show

46. Standardized Test Preparation Chapter C3 Reading Read each of the passages. Then, answer the questions that follow each passage.

47. Standardized Test Preparation Chapter C3 Passage 1The different versions of a gene are called alleles. When two different alleles occur together, one is often expressed while the other has no obvious effect on the organism’s appearance. The expressed form of the trait is dominant. The trait that was not expressed when the dominant form of the trait was present is called recessive. Imagine a plant that has both purple and white alleles for flower color. If the plant blooms purple, then purple is the dominant form of the trait. Therefore, white is the recessive form.

48. Standardized Test Preparation Chapter C3 1. According to the passage, which of the following statements is true? AAll alleles are expressed all of the time. BAll traits for flower color are dominant. CWhen two alleles are present, the expressed form of the trait is dominant. DA recessive form of a trait is always expressed.

49. Standardized Test Preparation Chapter C3 1. According to the passage, which of the following statements is true? AAll alleles are expressed all of the time. BAll traits for flower color are dominant. CWhen two alleles are present, the expressed form of the trait is dominant. DA recessive form of a trait is always expressed.

50. Standardized Test Preparation Chapter C3 2. According to the passage, a trait that is not expressed when the dominant form is present is called Frecessive. Gan allele. Hheredity. Ia gene.