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Chapter Eleven- Intro to Genetics

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Chapter Eleven Lecture- Intro to Genetics

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Chapter Eleven- Intro to Genetics

  1. 1. Copyright Pearson Prentice Hall biology
  2. 2. 11-1 The 11-1 Th eWo rWk of oGrergkor Moenfd eGl regor Mendel Copyright Pearson Prentice Hall
  3. 3. Gregor Mendel’s Peas Genetics is the scientific study of heredity. Gregor Mendel was an Austrian monk. His work was important to the understanding of heredity. Mendel carried out his work with ordinary garden peas. Copyright Pearson Prentice Hall Gregor Mendel’s Peas
  4. 4. Copyright Pearson Prentice Hall Gregor Mendel’s Peas Mendel knew that •the male part of each flower produces pollen, (containing sperm). •the female part of the flower produces egg cells.
  5. 5. Copyright Pearson Prentice Hall Gregor Mendel’s Peas During sexual reproduction, sperm and egg cells join in a process called fertilization. Fertilization- sperm and egg join to produce a new cell.
  6. 6. Copyright Pearson Prentice Hall Gregor Mendel’s Peas Pea flowers are self-pollinating. Sperm cells in pollen fertilize the egg cells in the same flower. The seeds that are produced by self-pollination inherit all of their characteristics from the single plant that bore them.
  7. 7. Copyright Pearson Prentice Hall Gregor Mendel’s Peas Mendel had true-breeding pea plants. True-breeding plants, if allowed to self-pollinate, produce offspring identical to themselves.
  8. 8. Copyright Pearson Prentice Hall Gregor Mendel’s Peas Mendel wanted to produce seeds by joining male and female reproductive cells from two different plants. He cut away the pollen-bearing male parts of the plant and dusted the plant’s flower with pollen from another plant.
  9. 9. Copyright Pearson Prentice Hall Gregor Mendel’s Peas This process is called cross-pollination. Cross-pollination produces seeds that have two different parents.
  10. 10. Copyright Pearson Prentice Hall Genes and Dominance A trait is a specific characteristic that varies from one individual to another.
  11. 11. Copyright Pearson Prentice Hall Genes and Dominance Mendel studied seven pea plant traits, each with two contrasting characters. He crossed plants with each of the seven contrasting characters and studied their offspring.
  12. 12. Copyright Pearson Prentice Hall Genes and Dominance Each original pair of plants is the P (parental) generation. The offspring are called the F1, or “first filial,” generation.
  13. 13. Copyright Pearson Prentice Hall Genes and Dominance The offspring of crosses between parents with different traits are called hybrids. The F1 hybrid plants all had the character of only one of the parents.
  14. 14. Mendel’s F1 Crosses on Pea Plants Copyright Pearson Prentice Hall
  15. 15. Mendel’s F1 Crosses on Pea Plants Mendel’s Seven F1 Crosses on Pea Plants Copyright Pearson Prentice Hall
  16. 16. Copyright Pearson Prentice Hall Genes and Dominance Mendel's first conclusion was that biological inheritance is determined by factors that are passed from one generation to the next. = genes!
  17. 17. Copyright Pearson Prentice Hall Genes and Dominance Each of the traits Mendel studied was controlled by one gene that occurred in two contrasting forms that produced different characters for each trait. The different forms of a gene are called alleles. Mendel’s second conclusion is called the principle of dominance.
  18. 18. Copyright Pearson Prentice Hall Genes and Dominance The principle of dominance states that some alleles are dominant and others are recessive.
  19. 19. Copyright Pearson Prentice Hall Genes and Dominance An organism with a dominant allele for a trait will always exhibit that form of the trait. An organism with the recessive allele for a trait will exhibit that form only when the dominant allele for that trait is not present.
  20. 20. Copyright Pearson Prentice Hall Genes and Dominance Pink x white = all pink Pink is dominant allele White is recessive allele
  21. 21. Copyright Pearson Prentice Hall
  22. 22. Copyright Pearson Prentice Hall Segregation Segregation Mendel crossed the F1 generation with itself to produce the F2 (second filial) generation. The traits controlled by recessive alleles reappeared in one fourth of the F2 plants.
  23. 23. Mendel's F2 Generation P Generation F1 Generation Segregation Tall Short Tall Tall Tall Tall Tall Short Copyright Pearson Prentice Hall F2 Generation
  24. 24. Copyright Pearson Prentice Hall Segregation Mendel assumed that the dominant allele masks the recessive allele in the F1 generation. The trait controlled by the recessive allele showed up in some of the F2 plants.
  25. 25. Copyright Pearson Prentice Hall Segregation The reappearance of the recessive trait showed that the allele for shortness had been separated, or segregated, from the allele for tallness.
  26. 26. Copyright Pearson Prentice Hall Segregation Mendel suggested that the alleles segregate from each other during the formation of the sex cells, or gametes.
  27. 27. Segregation When each F1 plant flowers and produces gametes, the two alleles segregate from each other so that each gamete carries only a single copy of each gene. Therefore, each F1 plant produces two types of gametes—those with the allele for tallness, and those with the allele for shortness. Copyright Pearson Prentice Hall
  28. 28. Copyright Pearson Prentice Hall Segregation Alleles separate during gamete formation.
  29. 29. 11-2 Probability and Punnett Squares 11-2 Probability and Punnett Squares Copyright Pearson Prentice Hall
  30. 30. Copyright Pearson Prentice Hall Genetics and Probability The likelihood that a particular event will occur is called probability. Probability can be used to predict the outcomes of genetic crosses.
  31. 31. Copyright Pearson Prentice Hall Punnett Squares Punnett squares are diagrams used to predict and compare the genetic variations that will result from a cross.
  32. 32. A capital letter represents the dominant allele. A lowercase letter represents the recessive allele. In this example, T = tall t = short Copyright Pearson Prentice Hall Punnett Squares
  33. 33. Copyright Pearson Prentice Hall Punnett Squares Gametes produced by each parent are shown along the top and left side.
  34. 34. Copyright Pearson Prentice Hall Punnett Squares Possible gene combinations for the offspring appear in the four boxes.
  35. 35. Punnett Squares Organisms that have two identical alleles for a particular trait are said to be homozygous. Organisms that have two different alleles for the same trait are heterozygous.
  36. 36. Copyright Pearson Prentice Hall Punnett Squares Homozygous organisms are true-breeding for a particular trait. Heterozygous organisms are hybrid for a particular trait.
  37. 37. Punnett Squares Offspring have the same phenotype if they show the same trait. Offspring have the same genotype if they have the same genetic makeup (alleles).
  38. 38. Copyright Pearson Prentice Hall Punnett Squares The plants have different genotypes (TT and Tt), but they have the same phenotype (tall). TT Homozygous Tt Active art Heterozygous
  39. 39. Copyright Pearson Prentice Hall Probability and Probability and Segregation Segregation •One fourth (1/4) of the F2 plants have two alleles for tallness (TT). • 2/4 or 1/2 have one allele for tall (T), and one for short (t). •One fourth (1/4) of the F2 have two alleles for short (tt).
  40. 40. Copyright Pearson Prentice Hall Probability and Segregation The ratio of plants showing the dominant phenotype (TT or Tt genotype) to those showing the recessive phenotype(tt genotype) plants is 3:1. The predicted ratio showed up in Mendel’s experiments indicating that segregation did occur.
  41. 41. Copyright Pearson Prentice Hall Probabilities Predict Averages Probabilities Predict Averages • Probabilities predict the average outcome of a large number of events. • Probability cannot predict the precise outcome of an individual event. • In genetics, the larger the number of offspring, the closer the resulting numbers will get to expected values.
  42. 42. 11-3 Exploring Mendelian Genetics 11–3 Exploring Mendelian Genetics Copyright Pearson Prentice Hall
  43. 43. Independent Assortment •To determine if the segregation of one pair of alleles affects the segregation of another pair of alleles, Mendel performed a two-factor cross. Copyright Pearson Prentice Hall Independent Assortment
  44. 44. Copyright Pearson Prentice Hall Independent Assortment The Two-Factor Cross: F1 •Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy). •All of the F1 offspring produced round yellow peas (RrYy).
  45. 45. Copyright Pearson Prentice Hall Independent Assortment The alleles for round (R) and yellow (Y) are dominant over the alleles for wrinkled (r) and green (y).
  46. 46. Copyright Pearson Prentice Hall Independent Assortment The Two-Factor Cross: F2 •Mendel crossed the heterozygous F1 plants (RrYy) with each other to determine if the alleles would segregate from each other in the F2 generation. • RrYy × RrYy
  47. 47. Independent Assortment For a two-factor F1 hybrid cross, the Punnett square predicts a 9 : 3 : 3 :1 ratio in the F2 generation.
  48. 48. In Mendel’s experiment, the F2 generation produced the following: • 9 seeds that were round and yellow • 3 seeds that were round and green • 3 seeds that were wrinkled and yellow • 1 seed that was wrinkled and green Copyright Pearson Prentice Hall Independent Assortment
  49. 49. The principle of independent assortment states that alleles for different traits can segregate independently during the formation of gametes. Genes that segregate independently do not influence each other's inheritance. Copyright Pearson Prentice Hall Independent Assortment
  50. 50. Mendel's experimental results were very close to the 9 : 3 : 3 : 1 ratio predicted by the Punnett square. Mendel had discovered the principle of independent assortment. Copyright Pearson Prentice Hall Independent Assortment Independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms.
  51. 51. Copyright Pearson Prentice Hall A Summary of Mendel's Principles A Summary of Mendel's Principles •Genes are passed from parents to their offspring. • If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive.
  52. 52. • In most sexually reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed. •The alleles for different genes usually segregate independently of one another. Copyright Pearson Prentice Hall A Summary of Mendel's Principles
  53. 53. Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.
  54. 54. Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Incomplete Dominance •When one allele is not completely dominant over another it is called incomplete dominance. •In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes.
  55. 55. Copyright Pearson Prentice Hall A cross between red (RR) and white (WW) four o’clock plants produces pink-colored flowers (RW). Beyond Dominant and Recessive Alleles WW RR
  56. 56. Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles •In codominance, both alleles contribute to the phenotype (like spots!). • In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers. •Heterozygous chickens are speckled with both black and white feathers. The black and white colors do not blend to form a new color, but appear separately.
  57. 57. Copyright Pearson Prentice Hall Beyond Dominant and Multiple Alleles •Genes that are controlled by more than two alleles are said to have multiple alleles. •An individual can’t have more than two alleles. However, more than two possible alleles can exist in a population. •A rabbit's coat color is determined by a single gene that has at least four different alleles.
  58. 58. Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Different combinations of alleles result in the colors shown here. Full color: ACHIihmbininacolah:yi lclaacn : :Cc ccChhc,ch C, ccoccrhh c,c cChhc,c hoh ,r ocrc hCcc KEY C = full color; dominant to all other alleles cch = chinchilla; partial defect in pigmentation; dominant to ch and c alleles ch = Himalayan; color in certain parts of the body; dominant to c allele c = albino; no color; recessive to all other alleles
  59. 59. Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles •Polygenic Traits •Traits controlled by two or more genes are said to be polygenic traits. •Skin color in humans is a polygenic trait controlled by more than four different genes.
  60. 60. Copyright Pearson Prentice Hall Applying Mendel's Principles Applying Mendel's Principles •Thomas Hunt Morgan used fruit flies to advance the study of genetics. •Morgan and others tested Mendel’s principles and learned that they applied to other organisms as well as plants.
  61. 61. Copyright Pearson Prentice Hall Applying Mendel's Principles Mendel’s principles can be used to study inheritance of human traits and to calculate the probability of certain traits appearing in the next generation.
  62. 62. Copyright Pearson Prentice Hall Genetics and the Environment Genetics and the Environment •Characteristics of any organism are determined by the interaction between genes and the environment.
  63. 63. Copyright Pearson Prentice Hall 11-4 Me1i1o-4s Miesiosis
  64. 64. Each organism must inherit a single copy of every gene from each of its “parents.” Gametes are formed by a process that separates the two sets of genes so that each gamete ends up with just one set. Copyright Pearson Prentice Hall
  65. 65. Copyright Pearson Prentice Hall Chromosome Number Chromosome Number Organisms have different numbers of chromosomes. A body cell in an adult fruit fly has 8 chromosomes: 4 from the fruit fly's male parent, and 4 from its female parent.
  66. 66. Copyright Pearson Prentice Hall Chromosome Number Chromosomes come in homologous pairs. Homologous chromosomes contain genes for the same traits. Each of the 4 chromosomes that came from the male parent has a homologous chromosome from the female parent.
  67. 67. Copyright Pearson Prentice Hall Chromosome Number A cell that contains both sets of homologous chromosomes is said to be diploid (2N). The number of chromosomes in a diploid cell is sometimes represented by the symbol 2N. For Drosophila, the diploid number is 8, which can be written as 2N=8.
  68. 68. Copyright Pearson Prentice Hall Chromosome Number The gametes of sexually reproducing organisms contain only a single set of chromosomes, and therefore only a single set of genes. Gametes are haploid (N), with only one set of the homologous chromosomes. Haploid cells are represented by the symbol N. For Drosophila, the haploid number is 4, which can be written as N=4.
  69. 69. Copyright Pearson Prentice Hall Phases of Meiosis Meiosis is a process of division in which the number of chromosomes per cell is cut in half. Diploid = 2 sets of each gene Haploid = half = one of each gene
  70. 70. •Meiosis involves two divisions, meiosis I and meiosis II. •The diploid cell that enters meiosis becomes 4 haploid cells. Copyright Pearson Prentice Hall Phases of Meiosis Movie
  71. 71. Copyright Pearson Prentice Hall Phases of Meiosis Meiosis I Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis Interphase I Meiosis I Movie
  72. 72. Copyright Pearson Prentice Hall Phases of Meiosis Cells undergo a round of DNA replication, forming duplicate chromosomes. Interphase I
  73. 73. Copyright Pearson Prentice Hall Phases of Meiosis During prophase of meiosis 1, each chromosome pairs with its corresponding homologous chromosome to form a tetrad. There are 4 chromatids in a tetrad. MEIOSIS I Prophase I
  74. 74. Copyright Pearson Prentice Hall Phases of Meiosis Movie •When tetrads form in prophase I, they exchange portions of their chromatids in a process called crossing over. • Crossing-over produces new combinations of alleles.
  75. 75. Copyright Pearson Prentice Hall Phases of Meiosis Spindle fibers attach to the chromosomes. MEIOSIS I Metaphase I
  76. 76. Copyright Pearson Prentice Hall Phases of Meiosis MEIOSIS I Anaphase I The fibers pull the homologous chromosomes toward opposite ends of the cell.
  77. 77. Copyright Pearson Prentice Hall Phases of Meiosis MEIOSIS I Telophase I and Cytokinesis Nuclear membranes form. The cell separates into two cells. The two cells produced by meiosis I have chromosomes and alleles that are different from each other and from the parent cell.
  78. 78. Copyright Pearson Prentice Hall Phases of Meiosis Meiosis II •The two cells produced by meiosis I now enter a second meiotic division. •Unlike meiosis I, neither cell goes through chromosome replication. •Each of the cell’s chromosomes has 2 chromatids.
  79. 79. Meiosis II Telophase I and Metaphase II Anaphase II Cytokinesis I Copyright Pearson Prentice Hall Phases of Meiosis Meiosis II Telophase II and Cytokinesis Prophase II Movie
  80. 80. Copyright Pearson Prentice Hall Phases of Meiosis Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original cell. MEIOSIS II Prophase II
  81. 81. Copyright Pearson Prentice Hall Phases of Meiosis The chromosomes line up in the center of cell. MEIOSIS II Metaphase II
  82. 82. Copyright Pearson Prentice Hall Phases of Meiosis The sister chromatids separate and move toward opposite ends of the cell. MEIOSIS II Anaphase II
  83. 83. Copyright Pearson Prentice Hall Phases of Meiosis Meiosis II results in four haploid (N) daughter cells. MEIOSIS II Telophase II and Cytokinesis Active art
  84. 84. Copyright Pearson Prentice Hall Gamete Formation Gamete Formation In male animals, meiosis results in four equal-sized gametes called sperm.
  85. 85. Copyright Pearson Prentice Hall Gamete Formation In many female animals, one egg and 3 polar bodies result from meiosis. The three cells, called polar bodies, are usually not involved in reproduction.
  86. 86. Copyright Pearson Prentice Hall Comparing Mitosis and Meiosis Comparing Mitosis and Meiosis Mitosis results in the production of two genetically identical diploid cells. Meiosis produces four genetically different haploid cells.
  87. 87. Copyright Pearson Prentice Hall Comparing Mitosis and Meiosis Mitosis •Cells produced by mitosis have the same number of chromosomes and alleles as the original cell. • Mitosis allows an organism to grow and replace cells. •Some organisms reproduce asexually by mitosis.
  88. 88. Copyright Pearson Prentice Hall Comparing Mitosis and Meiosis Meiosis •Cells produced by meiosis have half the number of chromosomes as the parent cell. •These cells are genetically different from the diploid cell and from each other. •Meiosis is how sexually-reproducing organisms produce gametes.
  89. 89. Copyright Pearson Prentice Hall Gene Linkage Thomas Hunt Morgan researched the genetics of fruit flies because they had many offspring in a short time.
  90. 90. 11-5 Linkage and Gene Maps 11-5 Linkage and Gene Maps Copyright Pearson Prentice Hall
  91. 91. Copyright Pearson Prentice Hall Gene Linkage Gene Linkage •Thomas Hunt Morgan’s research on fruit flies led him to the principle of linkage. •Morgan discovered that many of the more than 50 Drosophila genes he had identified appeared to be “linked” together. •They seemed to violate the principle of independent assortment.
  92. 92. Morgan and his associates grouped the linked genes into four linkage groups. Each linkage group assorted independently but all the genes in one group were inherited together. Each chromosome is actually a group of linked genes ( a linkage group). Copyright Pearson Prentice Hall Gene Linkage
  93. 93. Copyright Pearson Prentice Hall Gene Linkage Morgan concluded that Mendel’s principle of independent assortment still holds true. Chromosomes assort independently, not individual genes. Mendel did not observe gene linkage because the genes he studied happened to be on different chromosomes.
  94. 94. Copyright Pearson Prentice Hall Gene Maps Gene Maps •Crossing-over during meiosis sometimes separates genes that had been on the same chromosomes onto homologous chromosomes. •Crossover events can separate linked genes and produce new combinations of alleles.
  95. 95. Alfred Sturtevant, a student of Morgan, reasoned that the farther apart two linked genes are, the more likely they are to be separated due to crossover. Recombination frequencies can be used to determine the distance between genes. Copyright Pearson Prentice Hall Gene Maps
  96. 96. Sturtevant created a gene map of a Drosophila chromosome. A gene map shows the relative locations of each known gene on a chromosome. Copyright Pearson Prentice Hall Gene Maps
  97. 97. If two genes are close together, the recombination frequency between them should be low, since crossovers are rare. If they are far apart, recombination rates between them should be high. Copyright Pearson Prentice Hall Gene Maps
  98. 98. Exact location on chromosome Chromosome 2 0.0 Copyright Pearson Prentice Hall Gene Maps Aristaless (no bristles on antenna) 13.0 Dumpy wing 48.5 Black body 54.5 Purple eye 67.0 Vestigial (small) wing 99.2 Arc (bent wings) 107.0 Speck wing
  99. 99. Exact location on chromosome Chromosome 2 1.3 Star eye 31.0 Dachs (short legs) 51.0 Reduced bristles 55.0 Light eye 75.5 Curved wing 104.5 Brown eye Copyright Pearson Prentice Hall Gene Maps
  100. 100. Copyright Pearson Prentice Hall 11-1 Gametes are also known as a. genes. b. sex cells. c. alleles. d. hybrids.
  101. 101. Copyright Pearson Prentice Hall 11-1 The offspring of crosses between parents with different traits are called a. alleles. b. hybrids. c. gametes. d. dominant.
  102. 102. Copyright Pearson Prentice Hall 11-1 In a cross of a true-breeding tall pea plant with a true-breeding short pea plant, the F1 generation consists of a. all short plants. b. all tall plants. c. half tall plants and half short plants. d. all plants of intermediate height.
  103. 103. Copyright Pearson Prentice Hall 11-1 If a particular form of a trait is always present when the allele controlling it is present, then the allele must be a. mixed. b. recessive. c. hybrid. d. dominant.
  104. 104. Copyright Pearson Prentice Hall 11-2 Probability can be used to predict a. average outcome of many events. b. precise outcome of any event. c. how many offspring a cross will produce. d. which organisms will mate with each other.
  105. 105. Copyright Pearson Prentice Hall 11-2 Compared to 4 flips of a coin, 400 flips of the coin is a. more likely to produce about 50% heads and 50% tails. b. less likely to produce about 50% heads and 50% tails. c. guaranteed to produce exactly 50% heads and 50% tails. d. equally likely to produce about 50% heads and 50% tails.
  106. 106. Copyright Pearson Prentice Hall 11-2 Organisms that have two different alleles for a particular trait are said to be a. hybrid. b. heterozygous. c. homozygous. d. recessive.
  107. 107. Copyright Pearson Prentice Hall 11-2 Two F1 plants that are homozygous for shortness are crossed. What percentage of the offspring will be tall? a. 100% b. 50% c. 0% d. 25%
  108. 108. Copyright Pearson Prentice Hall 11-2 The Punnett square allows you to predict a. only the phenotypes of the offspring from a cross. b. only the genotypes of the offspring from a cross. c. both the genotypes and the phenotypes from a cross. d. neither the genotypes nor the phenotypes from a cross.
  109. 109. Copyright Pearson Prentice Hall 11–3 In a cross involving two pea plant traits, observation of a 9 : 3 : 3 : 1 ratio in the F2 generation is evidence for a. the two traits being inherited together. b. an outcome that depends on the sex of the parent plants. c. the two traits being inherited independently of each other. d. multiple genes being responsible for each trait.
  110. 110. Copyright Pearson Prentice Hall 11–3 In four o'clock flowers, the alleles for red flowers and white flowers show incomplete dominance. Heterozygous four o'clock plants have a. pink flowers. b. white flowers. c. half white flowers and half red flowers. d. red flowers.
  111. 111. Copyright Pearson Prentice Hall 11–3 A white male horse and a tan female horse produce an offspring that has large areas of white coat and large areas of tan coat. This is an example of a. incomplete dominance. b. multiple alleles. c. codominance. d. a polygenic trait.
  112. 112. Copyright Pearson Prentice Hall 11–3 Mendel's principles apply to a. pea plants only. b. fruit flies only. c. all organisms. d. only plants and animals.
  113. 113. Copyright Pearson Prentice Hall 11-4 If the body cells of humans contain 46 chromosomes, a single sperm cell should have a. 46 chromosomes. b. 23 chromosomes. c. 92 chromosomes. d. between 23 and 46 chromosomes.
  114. 114. Copyright Pearson Prentice Hall 11-4 During meiosis, the number of chromosomes per cell is cut in half through the separation of a. daughter cells. b. homologous chromosomes. c. gametes. d. chromatids.
  115. 115. Copyright Pearson Prentice Hall 11-4 The formation of a tetrad occurs during a. anaphase I. b. metaphase II. c. prophase I. d. prophase II.
  116. 116. Copyright Pearson Prentice Hall 11-4 In many female animals, meiosis results in the production of a. only 1 egg. b. 1 egg and 3 polar bodies. c. 4 eggs. d. 1 egg and 2 polar bodies.
  117. 117. Copyright Pearson Prentice Hall 11-4 Compared to egg cells formed during meiosis, daughter cells formed during mitosis are a. genetically different, while eggs are genetically identical. b. genetically different, just as egg cells are. c. genetically identical, just as egg cells are. d. genetically identical, while egg cells are genetically different.
  118. 118. Copyright Pearson Prentice Hall 11-5 According to Mendel's principle of independent assortment, the factors that assort independently are the a. genes. b. chromosomes. c. chromatids. d. gametes.
  119. 119. Copyright Pearson Prentice Hall 11-5 Linkage maps can be produced because the farther apart two genes are on a chromosome, a. the less likely they are to assort independently. b. the more likely they are to be linked. c. the more likely they are to be separated by a crossover. d. the less likely they are to be separated by a crossover.
  120. 120. Copyright Pearson Prentice Hall 11-5 If two genes are close together on the same chromosome, they are more likely to a. behave as though they are linked. b. behave independently. c. move to different chromosomes. d. belong to different linkage groups.

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