Chapter   11Introduction to   Genetics
11- 1 The Work of Gregor Mendel• Every living thing – plant or animal,  microbe or human being – has a set  of characteris...
Genetics• The scientific study of heredity
Gregor Mendel• Austrian Monk• Born 1822 in Czech  Republic• Worked at monastery  and taught high school• Tended the monast...
True breeding• If allowed to self pollinate they  would produce offspring identical  to themselves• He was also able to cr...
Genes and Dominance• Mendel studied seven different  pea plant traits• Each trait he studied had a  contrasting form
Pea Plant Traits
Genes and Dominance• The offspring of crosses between  parents with different traits are called  Hybrids• When Mendel cros...
Mendel drew two conclusions 1. Inheritance is determined by  factors that are passed from  generation to generation – toda...
Alleles• Different forms of a gene
Mendel’s 2 conclusion               nd2. The Principal of Dominance• Some alleles are dominant and  some are recessive
dominant• Covers up the recessive formEx.) T = tall
recessive• Gets covered up in the presence  of a dominant alleleEx.) t = short
Segregation• Mendel wanted to answer another  questionQ: Had the recessive alleles  disappeared? Or where they still  pres...
P1 Parental     F1            F2Tall   Short   All Tall   3 tall : 1 short                          75% tall              ...
The F1 Cross• The recessive traits reappeared!• Roughly 1/4 of the F2 plants  showed a recessive trait
Explanation of the F1 Cross• The reappearance indicated that at some point  the allele for shortness had been separated fr...
11-2 Probability and Punnett         Squares• Mendel kept obtaining similar  results, he soon realized that the  principal...
Probability• The likelihood that a particular  event will occur• The way in which alleles  segregate is random like a coin...
Punnett Square Vocab     If you do not know the  following vocabulary words      you will fail miserably
Punnett Square• Diagram used to determine  genetic crosses
Homozygous• Organisms that have 2 identicle  alleles for a traitEx.) TT , tt
Heterozygous• Have two different alleles for a  traitEx.) Tt
Phenotype• Physical characteristics – (words)Ex.) tall
Genotype• Genetic make-up - (letters)Ex.) Tt, TT, tt
11-3 ExploringMendelian Genetics
• Mendel wondered if alleles segregate  during the formation of gametes  independently• Does the segregation of one pair o...
All heterozygous   9:3:3:1 Ratio
Independent Assortment• Genes that segregate  independently do not influence  each others inheritance
A Summary of Mendel’s Principles• The inheritance of biological  characteristics is determined by  individual units known ...
A Summary of Mendel’s Principles• In cases in which 2 or more forms of a  gene are present, some forms of the gene  may be...
Incomplete Dominance• When one allele is not dominant  over another• Four o’clock flowers• The heterozygous phenotype is  ...
Codominance• When both alleles contribute to  the phenotype of an organismEx.) Speckled Chickens
Multiple Alleles• When more than two possible  alleles exist in a populationEx.) blood type• IA         Dominant• IB•i    ...
Human Blood TypesPhenotype   Genotype   A        IAIA or IAi   B        IBIB or IBi   AB          IA I B   O            ii
Polygenic Traits• Traits controlled by two or more  genesEx.) eye color, skin color
Genetics and the Environment• The characteristics of any organism,  is not only determined by the genes it  inherits• Char...
Do Now• Human hair is inherited by  incomplete dominance. Human  hair may be curly (CC) or straight  (cc). The heterozygou...
Do Now• A man is suing his wife on grounds of  infidelity. The man claims that the  child is blood type O and therefore  m...
11 – 4 Meiosis
Objectives• What happens during the events  of meiosis?• What is the difference between  mitosis and meiosis?
Meiosis• Gregor Mendel did not know  where the genes he had  discovered were located in the  cell• Genes are located on   ...
Mendel’s principles of genetics    require at least 2 things1. Each organism must inherit… a   single copy of every gene f...
Chromosome NumberEx.) fruit fly 8 chromosomes• 4 from mom, 4 from dadEx.) Humans 46 chromosomes• 23 from mom, 23 from dad
Homologous• Chromosomes that each have a  corresponding chromosome from  the opposite sex parent
Diploid• A cell that contains both sets  of homologous chromosomes  (2N) –Body cells
Haploid• A cell that contains only a single  set of chromosomes (1N)  – Sex cells (gametes)
Meiosis• A process of reduction division  in which the number of  chromosomes per cell is cut in  half through the separat...
Meiosis usually involves 2 divisions• Meiosis I• Meiosis II
Meiosis I• prior to meiosis I, each  chromosome is replicated• The cells then begin to divide  similar to mitosis
Prophase I• Each chromosome pairs with its  corresponding homologous  chromosome to form a structure  called a           T...
Crossing over• When chromosomes exchange  portions of their chromatids and  results in the exchange of alleles
Crossing over• Leads to new combinations of alleles• The homologous chromosomes separate,  and 2 new cells are formed• Alt...
Meiosis II• The two cells produced by  meiosis I now enter a second  meiotic division• Unlike the 1st division, no  chromo...
Metaphase II• 2 chromosomes line up in the  center of each cell
Anaphase II• The paired chromatids separate
Telophase II• Forms 4 daughter cells each with  2 chromatids• These 4 daughter cells are now  haploid (N) – just 2 chromos...
Gamete Formation• In male animals, the haploid  gametes produced by meiosis are  called sperm• In some plants they are cal...
Spermatogenesis
Gamete Formation• In females, generally only one of  the cells produced by meiosis is  involved in reproduction• This fema...
oogenisis
Comparing Mitosis and Meiosis• Mitosis results in the production of  two genetically identical diploid  cells, whereas mei...
Comparing Mitosis and Meiosis Mitosis            Meiosis     46                  4646        46   23   23        23   23
11-5 Linkage and  Gene Maps
Gene Linkage• When genes are located on the  same chromosome they are  inherited together (Linkage)• It’s the chromosomes ...
• When genes are formed on the same  chromosome, this does not mean that  they are linked forever• Crossing over during me...
Q: Why is this good?A: Generates genetic diversity
Gene Maps• 1911 Alfred Sturtevant• hypothesized that the further apart  genes were, the more likely they were  to be separ...
Gene map• Shows the location of each gene
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
Biology - Chp 11 - Introduction To Genetics - PowerPoint
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Biology - Chp 11 - Introduction To Genetics - PowerPoint

  1. 1. Chapter 11Introduction to Genetics
  2. 2. 11- 1 The Work of Gregor Mendel• Every living thing – plant or animal, microbe or human being – has a set of characteristics inherited from its parents• Since the beginning of recorded history, people have wanted to understand how that inheritance is passed from generation to generation
  3. 3. Genetics• The scientific study of heredity
  4. 4. Gregor Mendel• Austrian Monk• Born 1822 in Czech Republic• Worked at monastery and taught high school• Tended the monastery garden• Grew peas and became interested in the traits that were expressed in different generations of peas
  5. 5. True breeding• If allowed to self pollinate they would produce offspring identical to themselves• He was also able to cross breed peas for different traits
  6. 6. Genes and Dominance• Mendel studied seven different pea plant traits• Each trait he studied had a contrasting form
  7. 7. Pea Plant Traits
  8. 8. Genes and Dominance• The offspring of crosses between parents with different traits are called Hybrids• When Mendel crossed plants with different traits he expected them to blend, but that’s not what happened at all.• All of the offspring had the character of only one of the parents
  9. 9. Mendel drew two conclusions 1. Inheritance is determined by factors that are passed from generation to generation – today we call these factors genes
  10. 10. Alleles• Different forms of a gene
  11. 11. Mendel’s 2 conclusion nd2. The Principal of Dominance• Some alleles are dominant and some are recessive
  12. 12. dominant• Covers up the recessive formEx.) T = tall
  13. 13. recessive• Gets covered up in the presence of a dominant alleleEx.) t = short
  14. 14. Segregation• Mendel wanted to answer another questionQ: Had the recessive alleles disappeared? Or where they still present in the F1 plants?• To answer this he allowed the F1 plants to produce an F2 generation by self pollination
  15. 15. P1 Parental F1 F2Tall Short All Tall 3 tall : 1 short 75% tall 25% short
  16. 16. The F1 Cross• The recessive traits reappeared!• Roughly 1/4 of the F2 plants showed a recessive trait
  17. 17. Explanation of the F1 Cross• The reappearance indicated that at some point the allele for shortness had been separated from the allele for tallness• Mendel suggested that the alleles for tallness and shortness in the F1 plants were segregated from each other during the formation of sex cells or gametes• When each F1 plant flowers, 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
  18. 18. 11-2 Probability and Punnett Squares• Mendel kept obtaining similar results, he soon realized that the principals of probability could be used to explain the results of genetic crosses
  19. 19. Probability• The likelihood that a particular event will occur• The way in which alleles segregate is random like a coin flip
  20. 20. Punnett Square Vocab If you do not know the following vocabulary words you will fail miserably
  21. 21. Punnett Square• Diagram used to determine genetic crosses
  22. 22. Homozygous• Organisms that have 2 identicle alleles for a traitEx.) TT , tt
  23. 23. Heterozygous• Have two different alleles for a traitEx.) Tt
  24. 24. Phenotype• Physical characteristics – (words)Ex.) tall
  25. 25. Genotype• Genetic make-up - (letters)Ex.) Tt, TT, tt
  26. 26. 11-3 ExploringMendelian Genetics
  27. 27. • Mendel wondered if alleles segregate during the formation of gametes independently• Does the segregation of one pair of alleles affect the segregation of another pair of alleles?• For example, does the gene that determines whether round or wrinkled in shape have anything to do with the gene for color?• Must a round seed also be yellow?
  28. 28. All heterozygous 9:3:3:1 Ratio
  29. 29. Independent Assortment• Genes that segregate independently do not influence each others inheritance
  30. 30. A Summary of Mendel’s Principles• The inheritance of biological characteristics is determined by individual units known as _______________. In organisms Genes that reproduce sexually, _______________ are passed Genes from parents to offspring
  31. 31. A Summary of Mendel’s Principles• In cases in which 2 or more forms of a gene are present, some forms of the gene may be _______________________ or dominant ___________________________ recessive• In most sexually reproducing organisms, each adult has two copies of each gene – one from each parent. These genes are segregated from each other when gametes are formed• The alleles for different genes usually segregate independently of one another
  32. 32. Incomplete Dominance• When one allele is not dominant over another• Four o’clock flowers• The heterozygous phenotype is somewhat in-between the two homozygous phenotypes
  33. 33. Codominance• When both alleles contribute to the phenotype of an organismEx.) Speckled Chickens
  34. 34. Multiple Alleles• When more than two possible alleles exist in a populationEx.) blood type• IA Dominant• IB•i Recessive
  35. 35. Human Blood TypesPhenotype Genotype A IAIA or IAi B IBIB or IBi AB IA I B O ii
  36. 36. Polygenic Traits• Traits controlled by two or more genesEx.) eye color, skin color
  37. 37. Genetics and the Environment• The characteristics of any organism, is not only determined by the genes it inherits• Characteristics are determined by interactions between genes and the environment• Ex.) genes may affect a plants height but the same characteristic is influenced by climate, soil conditions and availability of water
  38. 38. Do Now• Human hair is inherited by incomplete dominance. Human hair may be curly (CC) or straight (cc). The heterozygous genotype (Cc) produces wavy hair. Show a cross between two parents with wavy hair
  39. 39. Do Now• A man is suing his wife on grounds of infidelity. The man claims that the child is blood type O and therefore must be fathered by someone else. Can he use this evidence in court if he and his wife both have heterozygous B genotypes?• Show the cross of the two parents
  40. 40. 11 – 4 Meiosis
  41. 41. Objectives• What happens during the events of meiosis?• What is the difference between mitosis and meiosis?
  42. 42. Meiosis• Gregor Mendel did not know where the genes he had discovered were located in the cell• Genes are located on chromosomes ______________________ in the cell ______________ nucleus
  43. 43. Mendel’s principles of genetics require at least 2 things1. Each organism must inherit… a single copy of every gene from each of its parents2. When an organism produces its own gametes… these two sets of genes must be separated from each other so that each gamete contains just one set of genes
  44. 44. Chromosome NumberEx.) fruit fly 8 chromosomes• 4 from mom, 4 from dadEx.) Humans 46 chromosomes• 23 from mom, 23 from dad
  45. 45. Homologous• Chromosomes that each have a corresponding chromosome from the opposite sex parent
  46. 46. Diploid• A cell that contains both sets of homologous chromosomes (2N) –Body cells
  47. 47. Haploid• A cell that contains only a single set of chromosomes (1N) – Sex cells (gametes)
  48. 48. Meiosis• A process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell –Makes sex cells
  49. 49. Meiosis usually involves 2 divisions• Meiosis I• Meiosis II
  50. 50. Meiosis I• prior to meiosis I, each chromosome is replicated• The cells then begin to divide similar to mitosis
  51. 51. Prophase I• Each chromosome pairs with its corresponding homologous chromosome to form a structure called a Tetrad _____________________ - has 4 chromatids
  52. 52. Crossing over• When chromosomes exchange portions of their chromatids and results in the exchange of alleles
  53. 53. Crossing over• Leads to new combinations of alleles• The homologous chromosomes separate, and 2 new cells are formed• Although each cell now has 4 chromatids something is different. Because each pair of homologous chromosomes was separated, neither of the daughter cells has two complete sets of chromosomes that it would have in a diploid cell• The two sets have been shuffled
  54. 54. Meiosis II• The two cells produced by meiosis I now enter a second meiotic division• Unlike the 1st division, no chromosomes are replicated• Each cell’s chromosomes has 2 chromatids
  55. 55. Metaphase II• 2 chromosomes line up in the center of each cell
  56. 56. Anaphase II• The paired chromatids separate
  57. 57. Telophase II• Forms 4 daughter cells each with 2 chromatids• These 4 daughter cells are now haploid (N) – just 2 chromosomes each
  58. 58. Gamete Formation• In male animals, the haploid gametes produced by meiosis are called sperm• In some plants they are called pollen
  59. 59. Spermatogenesis
  60. 60. Gamete Formation• In females, generally only one of the cells produced by meiosis is involved in reproduction• This female gamete is called an egg• The other 3 cells that do not receive as much cytoplasm as the egg are called polar bodies
  61. 61. oogenisis
  62. 62. Comparing Mitosis and Meiosis• Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells
  63. 63. Comparing Mitosis and Meiosis Mitosis Meiosis 46 4646 46 23 23 23 23
  64. 64. 11-5 Linkage and Gene Maps
  65. 65. Gene Linkage• When genes are located on the same chromosome they are inherited together (Linkage)• It’s the chromosomes that assort independently not individual genes
  66. 66. • When genes are formed on the same chromosome, this does not mean that they are linked forever• Crossing over during meiosis sometimes separates genes that had been on the same chromosome onto homologous chromosomes• Cross over events occasionally separate and exchange linked genes and produce new combinations of alleles
  67. 67. Q: Why is this good?A: Generates genetic diversity
  68. 68. Gene Maps• 1911 Alfred Sturtevant• hypothesized that the further apart genes were, the more likely they were to be separated by a crossover in meiosis• the rate at which linked genes were separated and recombined could then be used to produce a “map” of distances between genes
  69. 69. Gene map• Shows the location of each gene

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