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Introduction to Genetics Chapter 11
11- 1 The Work of Gregor Mendel <ul><li>Every living thing – plant or animal, microbe or human being – has a set of charac...
Genetics <ul><li>The scientific study of heredity </li></ul>
Gregor Mendel <ul><li>Austrian Monk </li></ul><ul><li>Born 1822 in Czech Republic </li></ul><ul><li>Worked at monastery an...
True breeding <ul><li>If allowed to self pollinate they would produce offspring identical to themselves </li></ul><ul><li>...
 
Genes and Dominance <ul><li>Mendel studied seven different pea plant traits </li></ul><ul><li>Each trait he studied had a ...
Pea Plant Traits
Genes and Dominance <ul><li>The offspring of crosses between parents with different traits are called  Hybrids </li></ul><...
 
Mendel drew two conclusions <ul><li>1. Inheritance is determined by factors that are passed from generation to generation ...
Alleles <ul><li>Different forms of a gene </li></ul>
Mendel’s 2 nd  conclusion <ul><li>2. The Principal of Dominance </li></ul><ul><li>Some alleles are dominant and some are r...
dominant <ul><li>Covers up the recessive form </li></ul><ul><li>Ex.) T = tall </li></ul>
recessive <ul><li>Gets covered up in the presence of a dominant allele </li></ul><ul><li>Ex.) t = short </li></ul>
Segregation <ul><li>Mendel wanted to answer another question </li></ul><ul><li>Q: Had the recessive alleles disappeared? O...
P 1  Parental Tall  Short All Tall F 1   F 2 3 tall : 1 short 75% tall 25% short
The F 1  Cross <ul><li>The recessive traits reappeared! </li></ul><ul><li>Roughly  1/4  of the F 2  plants showed a recess...
Explanation of the F 1  Cross <ul><li>The reappearance indicated that at some point the allele for shortness had been sepa...
 
11-2 Probability and Punnett Squares <ul><li>Mendel kept obtaining similar results, he soon realized that the principals o...
Probability <ul><li>The likelihood that a particular event will occur </li></ul><ul><li>The way in which alleles segregate...
Punnett Square Vocab If you do not know the following vocabulary  words you will fail miserably
Punnett Square <ul><li>Diagram used to determine genetic crosses </li></ul>
Homozygous <ul><li>Organisms that have 2 identicle alleles for a trait </li></ul><ul><li>Ex.) TT ,  tt </li></ul>
Heterozygous <ul><li>Have two different alleles for a trait </li></ul><ul><li>Ex.) Tt </li></ul>
Phenotype <ul><li>Physical characteristics – (words) </li></ul><ul><li>Ex.) tall </li></ul>
Genotype <ul><li>Genetic make-up - (letters) </li></ul><ul><li>Ex.) Tt, TT, tt </li></ul>
11-3  Exploring Mendelian Genetics
<ul><li>Mendel wondered if alleles segregate during the formation of gametes independently </li></ul><ul><li>Does the segr...
All heterozygous 9:3:3:1 Ratio
Independent Assortment <ul><li>Genes that segregate independently do not influence each others inheritance </li></ul>
A Summary of Mendel’s Principles <ul><li>The inheritance of biological characteristics is determined by individual units k...
A Summary of Mendel’s Principles <ul><li>In cases in which 2 or more forms of a gene are present, some forms of the gene m...
Incomplete Dominance <ul><li>When one allele is not dominant over another </li></ul><ul><li>Four o’clock flowers </li></ul...
 
Codominance <ul><li>When both alleles contribute to the phenotype of an organism </li></ul><ul><li>Ex.) Speckled Chickens ...
Multiple Alleles <ul><li>When more than two possible alleles exist in a population </li></ul><ul><li>Ex.) blood type </li>...
I A I A   or  I A i I B I B   or  I B i I A I B ii Genotype A B AB O Phenotype Human Blood Types
Polygenic Traits <ul><li>Traits controlled by two or more genes </li></ul><ul><li>Ex.) eye color, skin color </li></ul>
Genetics and the Environment <ul><li>The characteristics of any organism, is not only determined by the genes it inherits ...
Do Now <ul><li>Human hair is inherited by incomplete dominance. Human hair may be curly (CC) or straight (cc). The heteroz...
Do Now <ul><li>A man is suing his wife on grounds of infidelity. The man claims that the child is blood type O and therefo...
11 – 4 Meiosis
Objectives <ul><li>What happens during the events of meiosis? </li></ul><ul><li>What is the difference between mitosis and...
<ul><li>Gregor Mendel did not know where the genes he had discovered were located in the cell </li></ul><ul><li>Genes are ...
Mendel’s principles of genetics require at least 2 things <ul><li>Each organism must inherit…  a single copy of every gene...
Chromosome Number <ul><li>Ex.) fruit fly 8 chromosomes </li></ul><ul><li>4 from mom, 4 from dad </li></ul><ul><li>Ex.) Hum...
Homologous <ul><li>Chromosomes that each have a corresponding chromosome from the opposite sex parent </li></ul>
Diploid <ul><li>A cell that contains both sets of homologous chromosomes (2N) </li></ul><ul><ul><li>Body cells </li></ul><...
Haploid <ul><li>A cell that contains only a single set of chromosomes (1N) </li></ul><ul><ul><li>Sex cells (gametes) </li>...
Meiosis <ul><li>A process of reduction division in which the number of chromosomes per cell is cut in half through the sep...
 
 
 
 
Meiosis usually involves 2 divisions <ul><li>Meiosis I </li></ul><ul><li>Meiosis II </li></ul>
Meiosis I <ul><li>prior to meiosis I, each chromosome is replicated  </li></ul><ul><li>The cells then begin to divide simi...
Prophase I <ul><li>Each chromosome pairs with its corresponding homologous chromosome to form a structure called a _______...
Crossing over <ul><li>When chromosomes exchange portions of their chromatids and results in the exchange of alleles </li><...
 
Crossing over <ul><li>Leads to new combinations of alleles </li></ul><ul><li>The homologous chromosomes separate, and 2 ne...
Meiosis II <ul><li>The two cells produced by meiosis I now enter a second meiotic division </li></ul><ul><li>Unlike the 1s...
Metaphase II <ul><li>2 chromosomes line up in the center of each cell </li></ul>
Anaphase II <ul><li>The paired chromatids separate </li></ul>
Telophase II <ul><li>Forms 4 daughter cells each with 2 chromatids </li></ul><ul><li>These 4 daughter cells are now haploi...
Gamete Formation <ul><li>In male animals, the haploid gametes produced by meiosis are called  sperm </li></ul><ul><li>In s...
Spermatogenesis
Gamete Formation <ul><li>In females, generally only one of the cells produced by meiosis is involved in reproduction </li>...
oogenisis
Comparing Mitosis and Meiosis   <ul><li>Mitosis results in the production of two genetically identical diploid cells, wher...
Comparing Mitosis and Meiosis 46 46 46 46 23 23 23 23 Mitosis Meiosis
11-5 Linkage and Gene Maps
Gene Linkage <ul><li>When genes are located on the same chromosome they are inherited together (Linkage) </li></ul><ul><li...
<ul><li>When genes are formed on the same chromosome, this does not mean that they are linked forever </li></ul><ul><li>Cr...
Q: Why is this good? <ul><li>A: Generates genetic diversity </li></ul>
Gene Maps   <ul><li>1911 Alfred Sturtevant </li></ul><ul><li>hypothesized that the further apart genes were, the more like...
Gene map <ul><li>Shows the location of each gene </li></ul>
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Biology - Chp 11 - Introduction To Genetics - PowerPoint

  1. 1. Introduction to Genetics Chapter 11
  2. 2. 11- 1 The Work of Gregor Mendel <ul><li>Every living thing – plant or animal, microbe or human being – has a set of characteristics inherited from its parents </li></ul><ul><li>Since the beginning of recorded history, people have wanted to understand how that inheritance is passed from generation to generation </li></ul>
  3. 3. Genetics <ul><li>The scientific study of heredity </li></ul>
  4. 4. Gregor Mendel <ul><li>Austrian Monk </li></ul><ul><li>Born 1822 in Czech Republic </li></ul><ul><li>Worked at monastery and taught high school </li></ul><ul><li>Tended the monastery garden </li></ul><ul><li>Grew peas and became interested in the traits that were expressed in different generations of peas </li></ul>
  5. 5. True breeding <ul><li>If allowed to self pollinate they would produce offspring identical to themselves </li></ul><ul><li>He was also able to cross breed peas for different traits </li></ul>
  6. 7. Genes and Dominance <ul><li>Mendel studied seven different pea plant traits </li></ul><ul><li>Each trait he studied had a contrasting form </li></ul>
  7. 8. Pea Plant Traits
  8. 9. Genes and Dominance <ul><li>The offspring of crosses between parents with different traits are called Hybrids </li></ul><ul><li>When Mendel crossed plants with different traits he expected them to blend, but that’s not what happened at all. </li></ul><ul><li>All of the offspring had the character of only one of the parents </li></ul>
  9. 11. Mendel drew two conclusions <ul><li>1. Inheritance is determined by factors that are passed from generation to generation – today we call these factors genes </li></ul>
  10. 12. Alleles <ul><li>Different forms of a gene </li></ul>
  11. 13. Mendel’s 2 nd conclusion <ul><li>2. The Principal of Dominance </li></ul><ul><li>Some alleles are dominant and some are recessive </li></ul>
  12. 14. dominant <ul><li>Covers up the recessive form </li></ul><ul><li>Ex.) T = tall </li></ul>
  13. 15. recessive <ul><li>Gets covered up in the presence of a dominant allele </li></ul><ul><li>Ex.) t = short </li></ul>
  14. 16. Segregation <ul><li>Mendel wanted to answer another question </li></ul><ul><li>Q: Had the recessive alleles disappeared? Or where they still present in the F 1 plants? </li></ul><ul><li>To answer this he allowed the F 1 plants to produce an F 2 generation by self pollination </li></ul>
  15. 17. P 1 Parental Tall Short All Tall F 1 F 2 3 tall : 1 short 75% tall 25% short
  16. 18. The F 1 Cross <ul><li>The recessive traits reappeared! </li></ul><ul><li>Roughly 1/4 of the F 2 plants showed a recessive trait </li></ul>
  17. 19. Explanation of the F 1 Cross <ul><li>The reappearance indicated that at some point the allele for shortness had been separated from the allele for tallness </li></ul><ul><li>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 </li></ul><ul><li>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 </li></ul>
  18. 21. 11-2 Probability and Punnett Squares <ul><li>Mendel kept obtaining similar results, he soon realized that the principals of probability could be used to explain the results of genetic crosses </li></ul>
  19. 22. Probability <ul><li>The likelihood that a particular event will occur </li></ul><ul><li>The way in which alleles segregate is random like a coin flip </li></ul>
  20. 23. Punnett Square Vocab If you do not know the following vocabulary words you will fail miserably
  21. 24. Punnett Square <ul><li>Diagram used to determine genetic crosses </li></ul>
  22. 25. Homozygous <ul><li>Organisms that have 2 identicle alleles for a trait </li></ul><ul><li>Ex.) TT , tt </li></ul>
  23. 26. Heterozygous <ul><li>Have two different alleles for a trait </li></ul><ul><li>Ex.) Tt </li></ul>
  24. 27. Phenotype <ul><li>Physical characteristics – (words) </li></ul><ul><li>Ex.) tall </li></ul>
  25. 28. Genotype <ul><li>Genetic make-up - (letters) </li></ul><ul><li>Ex.) Tt, TT, tt </li></ul>
  26. 29. 11-3 Exploring Mendelian Genetics
  27. 30. <ul><li>Mendel wondered if alleles segregate during the formation of gametes independently </li></ul><ul><li>Does the segregation of one pair of alleles affect the segregation of another pair of alleles? </li></ul><ul><li>For example, does the gene that determines whether round or wrinkled in shape have anything to do with the gene for color? </li></ul><ul><li>Must a round seed also be yellow? </li></ul>
  28. 31. All heterozygous 9:3:3:1 Ratio
  29. 32. Independent Assortment <ul><li>Genes that segregate independently do not influence each others inheritance </li></ul>
  30. 33. A Summary of Mendel’s Principles <ul><li>The inheritance of biological characteristics is determined by individual units known as _______________. In organisms that reproduce sexually, _______________ are passed from parents to offspring </li></ul>Genes Genes
  31. 34. A Summary of Mendel’s Principles <ul><li>In cases in which 2 or more forms of a gene are present, some forms of the gene may be _______________________ or ___________________________ </li></ul><ul><li>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 </li></ul><ul><li>The alleles for different genes usually segregate independently of one another </li></ul>dominant recessive
  32. 35. Incomplete Dominance <ul><li>When one allele is not dominant over another </li></ul><ul><li>Four o’clock flowers </li></ul><ul><li>The heterozygous phenotype is somewhat in-between the two homozygous phenotypes </li></ul>
  33. 37. Codominance <ul><li>When both alleles contribute to the phenotype of an organism </li></ul><ul><li>Ex.) Speckled Chickens </li></ul>
  34. 38. Multiple Alleles <ul><li>When more than two possible alleles exist in a population </li></ul><ul><li>Ex.) blood type </li></ul><ul><li>I A </li></ul><ul><li>I B </li></ul><ul><li>i </li></ul>Dominant Recessive
  35. 39. I A I A or I A i I B I B or I B i I A I B ii Genotype A B AB O Phenotype Human Blood Types
  36. 40. Polygenic Traits <ul><li>Traits controlled by two or more genes </li></ul><ul><li>Ex.) eye color, skin color </li></ul>
  37. 41. Genetics and the Environment <ul><li>The characteristics of any organism, is not only determined by the genes it inherits </li></ul><ul><li>Characteristics are determined by interactions between genes and the environment </li></ul><ul><li>Ex.) genes may affect a plants height but the same characteristic is influenced by climate, soil conditions and availability of water </li></ul>
  38. 42. Do Now <ul><li>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 </li></ul>
  39. 43. Do Now <ul><li>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? </li></ul><ul><li>Show the cross of the two parents </li></ul>
  40. 44. 11 – 4 Meiosis
  41. 45. Objectives <ul><li>What happens during the events of meiosis? </li></ul><ul><li>What is the difference between mitosis and meiosis? </li></ul>
  42. 46. <ul><li>Gregor Mendel did not know where the genes he had discovered were located in the cell </li></ul><ul><li>Genes are located on ______________________ in the cell ______________ </li></ul>Meiosis chromosomes nucleus
  43. 47. Mendel’s principles of genetics require at least 2 things <ul><li>Each organism must inherit… a single copy of every gene from each of its parents </li></ul><ul><li>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 </li></ul>
  44. 48. Chromosome Number <ul><li>Ex.) fruit fly 8 chromosomes </li></ul><ul><li>4 from mom, 4 from dad </li></ul><ul><li>Ex.) Humans 46 chromosomes </li></ul><ul><li>23 from mom, 23 from dad </li></ul>
  45. 49. Homologous <ul><li>Chromosomes that each have a corresponding chromosome from the opposite sex parent </li></ul>
  46. 50. Diploid <ul><li>A cell that contains both sets of homologous chromosomes (2N) </li></ul><ul><ul><li>Body cells </li></ul></ul>
  47. 51. Haploid <ul><li>A cell that contains only a single set of chromosomes (1N) </li></ul><ul><ul><li>Sex cells (gametes) </li></ul></ul>
  48. 52. Meiosis <ul><li>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 </li></ul><ul><ul><li>Makes sex cells </li></ul></ul>
  49. 57. Meiosis usually involves 2 divisions <ul><li>Meiosis I </li></ul><ul><li>Meiosis II </li></ul>
  50. 58. Meiosis I <ul><li>prior to meiosis I, each chromosome is replicated </li></ul><ul><li>The cells then begin to divide similar to mitosis </li></ul>
  51. 59. Prophase I <ul><li>Each chromosome pairs with its corresponding homologous chromosome to form a structure called a _____________________ - has 4 chromatids </li></ul>Tetrad
  52. 60. Crossing over <ul><li>When chromosomes exchange portions of their chromatids and results in the exchange of alleles </li></ul>
  53. 62. Crossing over <ul><li>Leads to new combinations of alleles </li></ul><ul><li>The homologous chromosomes separate, and 2 new cells are formed </li></ul><ul><li>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 </li></ul><ul><li>The two sets have been shuffled </li></ul>
  54. 63. Meiosis II <ul><li>The two cells produced by meiosis I now enter a second meiotic division </li></ul><ul><li>Unlike the 1st division, no chromosomes are replicated </li></ul><ul><li>Each cell’s chromosomes has 2 chromatids </li></ul>
  55. 64. Metaphase II <ul><li>2 chromosomes line up in the center of each cell </li></ul>
  56. 65. Anaphase II <ul><li>The paired chromatids separate </li></ul>
  57. 66. Telophase II <ul><li>Forms 4 daughter cells each with 2 chromatids </li></ul><ul><li>These 4 daughter cells are now haploid (N) – just 2 chromosomes each </li></ul>
  58. 67. Gamete Formation <ul><li>In male animals, the haploid gametes produced by meiosis are called sperm </li></ul><ul><li>In some plants they are called pollen </li></ul>
  59. 68. Spermatogenesis
  60. 69. Gamete Formation <ul><li>In females, generally only one of the cells produced by meiosis is involved in reproduction </li></ul><ul><li>This female gamete is called an egg </li></ul><ul><li>The other 3 cells that do not receive as much cytoplasm as the egg are called polar bodies </li></ul>
  61. 70. oogenisis
  62. 71. Comparing Mitosis and Meiosis <ul><li>Mitosis results in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells </li></ul>
  63. 72. Comparing Mitosis and Meiosis 46 46 46 46 23 23 23 23 Mitosis Meiosis
  64. 73. 11-5 Linkage and Gene Maps
  65. 74. Gene Linkage <ul><li>When genes are located on the same chromosome they are inherited together (Linkage) </li></ul><ul><li>It’s the chromosomes that assort independently not individual genes </li></ul>
  66. 75. <ul><li>When genes are formed on the same chromosome, this does not mean that they are linked forever </li></ul><ul><li>Crossing over during meiosis sometimes separates genes that had been on the same chromosome onto homologous chromosomes </li></ul><ul><li>Cross over events occasionally separate and exchange linked genes and produce new combinations of alleles </li></ul>
  67. 76. Q: Why is this good? <ul><li>A: Generates genetic diversity </li></ul>
  68. 77. Gene Maps <ul><li>1911 Alfred Sturtevant </li></ul><ul><li>hypothesized that the further apart genes were, the more likely they were to be separated by a crossover in meiosis </li></ul><ul><li>the rate at which linked genes were separated and recombined could then be used to produce a “map” of distances between genes </li></ul>
  69. 78. Gene map <ul><li>Shows the location of each gene </li></ul>
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