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Chapter 11: Introduction to Genetics

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  • 1. Analyzing Inheritance
    • Offspring resemble their parents. Offspring inherit genes for characteristics from their parents. To learn about inheritance, scientists have experimented with breeding various plants and animals.
    • In each experiment shown in the table on the next slide, two pea plants with different characteristics were bred. Then, the offspring produced were bred to produce a second generation of offspring. Consider the data and answer the questions that follow.
    Section 11-1 Interest Grabber
  • 2.
    • 1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
    • 2. How do the characteristics of the second generation compare to the characteristics of the first generation?
    Section 11-1 Interest Grabber continued Parents Long stems  short stems Red flowers  white flowers Green pods  yellow pods Round seeds  wrinkled seeds Yellow seeds  green seeds First Generation All long All red All green All round All yellow Second Generation 787 long: 277 short 705 red: 224 white 428 green: 152 yellow 5474 round: 1850 wrinkled 6022 yellow: 2001 green
  • 3.
    • 11–1 The Work of Gregor Mendel
      • A. Gregor Mendel’s Peas
      • B. Genes and Dominance
      • C. Segregation
        • 1. The F 1 Cross
        • 2. Explaining the F 1 Cross
    Section 11-1 Section Outline
  • 4. A. Mendel’s First Experiments
    • 1. Looked at 7 traits of pea plants
    • 2. Cross pollinated true-breeding (purebred) plants with the 7 contrasting characteristics (P generation)
    • a. Ex. Tall pea plant crossed (TT) with a short (tt)
    • 3. Studied the offspring (F1 generation)
    • a. Offspring are termed hybrids
    • i. Offspring of parents with different traits
    • b. All the offspring had the characteristics of only 1 of the parents
    • i. Ex. F1 were all tall
  • 5.
    • 4. Mendel drew 2 conclusions:
    • a. Inheritance determined by factors (now genes) passed on from 1 generation to the next
    • b. Principle of Dominance – some alleles are dominant and others are recessive
  • 6. Punnett Square: Cross of P Generation
  • 7. B. Mendel’s Next Experiments
    • 1. Wanted to answer: What happened to the recessive allele?
    • 2. Allowed the F1 generation to self-pollinate
    • a. Ex. Tall (Tt) x tall (Tt)
    • 3. Results were:
    • a. The recessive trait reappeared
  • 8.
    • 4. Explanation:
    • a. Alleles separate or segregate during the formation of gametes (sex cells)
    • b. The alleles separate so that each gamete carries 1 copy of each gene
    • c. Each F1 plant made 2 types of gametes
    • i. 1 for tallness
    • ii. 1 for shortness
    • Mendel's laws of genetic inheritance
  • 9. Punnett Square: Cross of F1 Generation
  • 10. P Generation F 1 Generation F 2 Generation Tall Short Tall Tall Tall Tall Tall Short Section 11-1 Principles of Dominance
  • 11. P Generation F 1 Generation F 2 Generation Tall Short Tall Tall Tall Tall Tall Short Section 11-1 Principles of Dominance
  • 12. P Generation F 1 Generation F 2 Generation Tall Short Tall Tall Tall Tall Tall Short Section 11-1 Principles of Dominance
  • 13. Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short Yellow Gray Smooth Green Axial Tall Section 11-1 Figure 11-3 Mendel’s Seven F 1 Crosses on Pea Plants
  • 14. Tossing Coins
    • If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin
    • ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.
    Section 11-2 Interest Grabber
  • 15. 1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected? 2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected? 3. If you compiled the results for the whole class, what results would you expect? 4. How do the expected results differ from the observed results? Section 11-2 Interest Grabber continued
  • 16.
    • 11–2 Probability and Punnett Squares
      • A. Genetics and Probability
      • B. Punnett Squares
      • C. Probability and Segregation
      • D. Probabilities Predict Averages
    Section 11-2 Section Outline
  • 17. Section 11-2 Tt X Tt Cross
  • 18. Section 11-2 Tt X Tt Cross
  • 19. Height in Humans
    • Height in pea plants is controlled by one of two alleles; the allele for a tall plant is the dominant allele, while the allele for a short plant is the ecessive one. What about people? Are the factors that determine height more complicated in humans?
    Section 11-3 Interest Grabber
  • 20.
    • 1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches.
    • 2. What can you observe about the heights of the ten people?
    • 3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.
    Section 11-3 Interest Grabber continued
  • 21.
    • 11–3 Exploring Mendelian Genetics
      • A. Independent Assortment
        • 1. The Two-Factor Cross: F 1
        • 2. The Two-Factor Cross: F 2
      • B. A Summary of Mendel’s Principles
      • C. Beyond Dominant and Recessive Alleles
        • 1. Incomplete Dominance
        • 2. Codominance
        • 3. Multiple Alleles
        • 4. Polygenic Traits
      • D. Applying Mendel’s Principles
      • E. Genetics and the Environment
    Section 11-3 Section Outline
  • 22. A. Independent Assortment
    • 1. Gene’s that separate independently do NOT influence each other’s inheritance
    • 2. Genes separate on their own when gametes are being made
    • 3. Two-factor cross used to support this
    • a. Using 2 different genes
  • 23. Section 11-3 Figure 11-10 Independent Assortment in Peas
  • 24. concluded that which is called the which is called the Gregor Mendel Section 11-3 Concept Map experimented with Law of Dominance Law of Segregation Pea plants “ Factors” determine traits Some alleles are dominant, and some alleles are recessive Alleles are separated during gamete formation
  • 25. B. Beyond Dominant and Recessive Alleles
    • 1. Incomplete Dominance
    • a. One allele is NOT completely dominant over the other
    • b. The heterozygous offspring is somewhere in between the homozygous parents
  • 26. Section 11-3 Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
  • 27. Section 11-3 Figure 11-11 Incomplete Dominance in Four O’Clock Flowers
  • 28.
    • 2. Codominance
    • a. Both alleles contribute to the heterozygous phenotype
    • b. Both alleles can be seen, for example
    • i. Spots on cows
    • ii. Speckled feathers on chickens
    • 3. Multiple Alleles
    • a. Genes with more than 2 alleles
    • b. Organisms still only have 2 of the alleles, there are just more than 2 options
    • c. Ex. Human blood types
    • i. A
    • ii. B
    • iii. AB
    • i. O
  • 29.
    • 4. Polygenic Traits
    • a. Traits controlled by more 2 or more genes
    • b. Ex. Skin color in humans
    • i. 4 different genes interacting
  • 30. How Many Chromosomes?
    • Normal human body cells each contain 46 chromosomes. The cell division process that body cells undergo is called mitosis and produces daughter cells that are virtually identical to the parent cell. Working with a partner, discuss and answer the questions that follow.
    Section 11-4 Interest Grabber
  • 31.
    • 1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?
    • 2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?
    • 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?
    Section 11-4 Interest Grabber continued
  • 32.
    • 11–4 Meiosis
      • A. Chromosome Number
      • B. Phases of Meiosis
        • 1. Meiosis I
        • 2. Meiosis II
      • C. Gamete Formation
      • D. Comparing Mitosis and Meiosis
    Section 11-4 Section Outline
  • 33. A. Meiosis and Mendel
    • 1. Mendel’s principles of genetics require 2 things
    • a. Offspring inherit a single copy of every gene from each parent
    • b. The 2 sets of genes must separate somehow so that each new gamete contains 1 set of genes
  • 34. B. Chromosomes
    • 1. Homologous
    • a. Corresponding chromosomes, 1 from the male parent and 1 from the female parent
  • 35. B. Chromosomes cont.
    • 2. Diploid cell
    • a. Contains 2 sets of chromosomes, so 2 sets of genes
    • b. Written as 2N
    • c. Describes cells at the start of meiosis
    • 3. Haploid cell
    • a. Contain 1 set of chromosomes, 1 set of genes
    • b. Written as N
    • c. Describes the gamete cells at the end of meiosis
  • 36. C. Overview of Meiosis
    • 1. Parent cells are diploid
    • 2. New gamete cells that are formed are haploid
    • 3. Reduction process where the number of chromosomes per cell is cut in half
    • 4. 2 divisions
    • a. Meiosis I
    • b. Meiosis II
    • 5. Result is 4 haploid cells genetically DIFFERENT from one another and the parent cell
  • 37. D. Phases of Meiosis
    • 1. Interphase (before meiosis I)
    • a. Each chromosome is replicated
    • 2. Meiosis I
    • a. Similar to mitosis (PMAT)
    • b. Prophase I
    • i. Each chromosome finds its homologous pair to form a tetrad
    • ii. During this pairing up, homologous chromosomes undergo crossing over – a piece of a chromatid is exchanged between the pairs
  • 38. Section 11-4 Crossing-Over
  • 39. Section 11-4 Crossing-Over
  • 40. Section 11-4 Crossing-Over
  • 41. Meiosis I cont.
    • c. Metaphase I and Anaphase look at diagram
    • d. Telophase I
    • i. 2 haploid cells
    • ii. Both with different alleles & chromosomes from each other because of crossing over
    • iii. These 2 cells go on to Meiosis II
  • 42. Meiosis I Section 11-4 Figure 11-15 Meiosis
  • 43. Meiosis I Section 11-4 Figure 11-15 Meiosis Meiosis I
  • 44. Meiosis I Section 11-4 Figure 11-15 Meiosis Meiosis I
  • 45. Section 11-4 Figure 11-15 Meiosis Meiosis I
  • 46. Section 11-4 Figure 11-15 Meiosis Meiosis I
  • 47. D. Phases of Meiosis cont.
    • 3. Meiosis II
    • a. 2 cells made in Meiosis 1 go through another division
    • b. NO chromosome replication
    • i. Reason WHY the 4 daughter cells are genetically different
    • c. Prophase II
  • 48. D. Phases of meiosis cont.
    • 3. Meioisis II cont.
    • d. Metaphase II
    • i. Sister chromatids line up in middle
    • e. Anaphase II
    • i. Sister chromatids split
    • f. Telophase II and Cytokinesis
    • i. 4 haploid cells
  • 49. Meiosis II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase II Metaphase II Anaphase II Telophase II The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells. Section 11-4 Figure 11-17 Meiosis II
  • 50. Meiosis II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase II Metaphase II Anaphase II Telophase II The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells. Section 11-4 Figure 11-17 Meiosis II
  • 51. Meiosis II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase II Metaphase II Anaphase II Telophase II The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells. Section 11-4 Figure 11-17 Meiosis II
  • 52. Meiosis II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase II Metaphase II Anaphase II Telophase II The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells. Section 11-4 Figure 11-17 Meiosis II
  • 53. Meiosis II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. Prophase II Metaphase II Anaphase II Telophase II The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells. Section 11-4 Figure 11-17 Meiosis II
  • 54.
    • Meiosis Animation
    • Meiosis v. Mitosis
  • 55. Forever Linked?
    • Some genes appear to be inherited together, or “linked.” If two genes
    • are found on the same chromosome, does it mean they are linked forever?
    • Study the diagram, which shows four genes labeled A–E and a–e, and then answer the questions on the next slide.
    Section 11-5 Interest Grabber
  • 56.
    • 1. In how many places can crossing over result in genes A and b being on the same chromosome?
    • 2. In how many places can crossing over result in genes A and c being on the same chromosome? Genes A and e?
    • 3. How does the distance between two genes on a chromosome affect the chances that crossing over will recombine those genes?
    Section 11-5 Interest Grabber continued
  • 57.
    • 11–5 Linkage and Gene Maps
      • A. Gene Linkage
      • B. Gene Maps
    Section 11-5 Section Outline
  • 58. Earth Country State City People Cell Chromosome Chromosome fragment Gene Nucleotide base pairs Section 11-5 Comparative Scale of a Gene Map Mapping of Earth’s Features Mapping of Cells, Chromosomes, and Genes
  • 59. Exact location on chromosomes Chromosome 2 Section 11-5 Figure 11-19 Gene Map of the Fruit Fly
  • 60. Video Contents
    • Click a hyperlink to choose a video.
    • Meiosis Overview
    • Animal Cell Meiosis, Part 1
    • Animal Cell Meiosis, Part 2
    • Segregation of Chromosomes
    • Crossing Over
    Videos
  • 61. Video 1
    • Click the image to play the video segment.
    Video 1 Meiosis Overview
  • 62. Video 2
    • Click the image to play the video segment.
    Video 2 Animal Cell Meiosis, Part 1
  • 63. Video 3
    • Click the image to play the video segment.
    Video 3 Animal Cell Meiosis, Part 2
  • 64. Video 4
    • Click the image to play the video segment.
    Video 4 Segregation of Chromosomes
  • 65. Video 5
    • Click the image to play the video segment.
    Video 5 Crossing Over
  • 66. Internet
    • The latest discoveries in genetics
    • Interactive test
    • Articles on genetics
    • For links on Punnett squares, go to www.SciLinks.org and enter the Web Code as follows: cbn-4112.
    • For links on Mendelian genetics, go to www.SciLinks.org and enter the Web Code as follows: cbn-4113.
    • For links on meiosis, go to www.SciLinks.org and enter the Web Code as follows: cbn-4114.
    Go Online
  • 67. Section 1 Answers
    • 1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
    • All offspring had the same characteristic, which was like one of the parents’. The other characteristic seemed to have disappeared.
    • 2. How do the characteristics of the second generation compare to the characteristics of the first generation?
    • Both characteristics appeared in this generation. The characteristic that had “disappeared” in the first generation did not appear as often as the other characteristic. (It appears about 25 percent of the time.)
    Interest Grabber Answers
  • 68. Section 2 Answers Interest Grabber Answers 1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected? Results will vary, but should be close to 5 heads and 5 tails. 2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected? The results for 20 tosses may be closer to the predicted 10 heads and 10 tails. 3. If you compiled the results for the whole class, what results would you expect? The results for the entire class should be even closer to the number predicted by the rules of probability. 4. How do the expected results differ from the observed results? The observed results are usually slightly different from the expected results.
  • 69. Section 3 Answers
    • 1. Make a list of 10 adults whom you know. Next to the name of each adult, write his or her approximate height in feet and inches.
    • Check students’ answers to make sure they are realistic.
    • 2. What can you observe about the heights of the ten people?
    • Students should notice that there is a range of heights in humans.
    • 3. Do you think height in humans is controlled by 2 alleles, as it is in pea plants? Explain your answer.
    • No, height does not seem to be controlled by two alleles, as it is in pea plants. Height in humans can vary greatly and is not just found in tall and short phenotypes.
    Interest Grabber Answers
  • 70. Section 4 Answers
    • 1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis?
    • 46 chromosomes
    • 2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo?
    • 46 + 46 = 92; a developing embryo would not survive if it contained 92 chromosomes.
    • 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have?
    • Sperm and egg should each have 23 chromosomes.
    Interest Grabber Answers
  • 71. Section 5 Answers
    • 1. In how many places can crossing over result in genes A and b being on the same chromosome?
    • One (between A and B)
    • 2. In how many places can crossing over result in genes A and c being on the same chromosome? Genes A and e?
    • Two (between A and B and A and C); Four (between A and B, A and C, A and D, and A and E)
    • 3. How does the distance between two genes on a chromosome affect the chances that crossing over will recombine those genes?
    • The farther apart the genes are, the more likely they are to be recombined through crossing over.
    Interest Grabber Answers
  • 72. End of Custom Shows
    • This slide is intentionally blank.