Classical Genetics Lecture


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Classical Genetics Lecture

  1. 1. Classical Genetics
  2. 2. The Work and Conclusions of Gregor Mendel Father of genetics Monk in Austria 1865 Studied patterns of inheritance in peas
  3. 3. Why Peas?
  4. 4. Why Peas? Self-fertilization produces true breeding generations
  5. 5. <ul><li>Prevented self-fertilization </li></ul><ul><li>Manipulated reproduction </li></ul><ul><li>Began monohybrid crosses </li></ul><ul><li>Carefully examined results </li></ul>Why Peas? Read Concept 1 Click Animation and View
  6. 6. Why Peas? Read Concept 2 Click Animation and View
  7. 7. Mendel’s Work Some traits are dominant and some are recessive Read concept 3 Click animation and view Read concept 4 Click animation and view
  8. 8. Mendel’s Work <ul><li>Traits are passed on by factors (genes) </li></ul><ul><li>Factors (genes) have more than 1 form called alleles </li></ul><ul><li>There are at least 2 alleles for each trait </li></ul>
  9. 9. Mendel’s Work Alleles are represented by the first letter of the dominant trait Pea plant flower color (trait) Purple or white Purple is dominant over white Alleles are represented as P=purple p=white
  10. 10. <ul><li>You try a few… </li></ul><ul><li>Round seeds are dominant over wrinkled seeds </li></ul><ul><li>Yellow seeds are dominant over green seeds </li></ul><ul><li>Tall plants are dominant over short plants </li></ul><ul><li>1. R=round r=wrinkled </li></ul><ul><li>Y=yellow y=green </li></ul><ul><li>T=tall t= short </li></ul>Mendel’s Work
  11. 11. Mendel’s Work Describing Traits (Tall or short plants) Genotype The actual genetic make-up of an organism the “genes” Phenotype The physical appearance or form observed the “physical”
  12. 12. Mendel’s Work Possible Genotypes (TT Tt tt) Homozygous The two alleles for the trait are identical TT homozygous dominant (purebred dominant) tt homozygous recessive (purebred recessive) Heterozygous The two alleles for the trait are different Tt heterozygote (hybrid)
  13. 13. Mendel’s Work
  14. 14. Mendel’s Work Read Concept 5 Click animation and view Complete visual organizer of Mendel’s pea plant experiment
  15. 15. 1. Law of Dominance Alleles for a trait are either dominant or recessive The dominant form is expressed and the recessive form is hidden The only way to express a recessive trait is if there are two copies of the recessive allele Mendel’s Conclusions
  16. 17. Mendel’s Conclusions <ul><li>Law of Segregation </li></ul><ul><li>The two alleles for a trait separate during gametogenesis </li></ul>
  17. 18. Test Cross
  18. 19. Dihybrid Cross
  19. 20. Mendel’s 3 rd Law of Independent Assortment <ul><li>Alleles of different genes are assorted independently of one another during the formation of gametes </li></ul><ul><li>This means that calculating the probability of several traits appearing together is the product of the probability of each trait taken separately </li></ul><ul><li>The Rule of Multiplication </li></ul>
  20. 21. Incomplete Dominance
  21. 22. “ Dominant” gene does not fully express itself to mask the effect of the recessive gene A pattern of inheritance in which the phenotype of a heterozygous individual is intermediate between those of the parents Genotypic ratio is equal to phenotypic ratio
  22. 23. Co-Dominance Two or more alleles are fully dominant When present together they are both expressed ABO Blood Groups exhibit co-dominace
  23. 24. Type A Blood <ul><li>• Individuals with group A blood have red blood </li></ul><ul><li>cells with antigen A on their surface. </li></ul><ul><li>Produce antibodies against antigen B, </li></ul><ul><li>antibody B. </li></ul><ul><li>• Therefore, a group A person can only receive </li></ul><ul><li>blood from people in groups A or O </li></ul>
  24. 25. Type B Blood <ul><li>Antigen B is on their cells, and antibodies A are produced in their serum. </li></ul><ul><li>A group B person can only receive blood from people in groups B or O, preferably B. </li></ul>
  25. 26. Type AB <ul><li>Individuals with group AB blood have red blood cells with both antigens A and B. </li></ul><ul><li>Do not produce antibodies A or B against either antigen in their serum. </li></ul><ul><li>A person with type AB blood can receive blood from any group (preferably AB) but cannot donate blood except to another AB (universal recipient). </li></ul>
  26. 27. Type O <ul><li>Individuals with group O blood have red blood cells with neither antigen A or B. </li></ul><ul><li>Produce antibodies A and B against both types of antigens. </li></ul><ul><li>A group O person can only receive blood from group O (universal donor). </li></ul>
  27. 32. Sex Inheritance Sex Chromosomes X or Y XX is female XY is male Read concept 9 Click animation and view
  28. 33. Sex-Linked Inheritance Genes linked to sex chromosomes
  30. 35. Sources of Genetic Disorders <ul><li>Chromosome Mutations </li></ul><ul><ul><ul><li>Change in the genetic material on the chromosome </li></ul></ul></ul><ul><ul><ul><li>Four types of chromosome mutations </li></ul></ul></ul><ul><ul><ul><ul><li>Deletion, duplication, translocation and inversion </li></ul></ul></ul></ul><ul><li>Change in chromosome number </li></ul><ul><ul><ul><li>Failure of homologous chromosomes to separate during meiosis </li></ul></ul></ul><ul><ul><ul><ul><li>Non-Disjunction </li></ul></ul></ul></ul>
  31. 36. Deletion <ul><li>One or more genes are lost from a chromosome during division </li></ul><ul><li>Occurs if homologous chromosomes cross over unequally during meiosis </li></ul>
  32. 37. Duplication <ul><li>Chromosome receives an extra piece, which duplicates some genes </li></ul>
  33. 38. Translocation <ul><li>A whole chromosome or piece of chromosome attaches to a chromosome in a different pair </li></ul><ul><li>Results in extra or lost genes </li></ul><ul><li>May break up important gene arrangements and change the phenotype of the organism </li></ul>
  34. 39. Inversion <ul><li>Part of chromosome breaks off and reattaches itself in reverse order </li></ul><ul><li>May cause no change because it is not losing genes </li></ul><ul><li>Changes the arrangement and may upset important gene interactions </li></ul>
  35. 41. Nondisjunction <ul><li>Failure of chromosome to separate during division </li></ul><ul><ul><li>Mitosis </li></ul></ul><ul><ul><ul><li>Cell dies, organism is not harmed </li></ul></ul></ul><ul><ul><li>Meiosis </li></ul></ul><ul><ul><ul><li>Results in an abnormal gamete that will produce abnormal offspring </li></ul></ul></ul>
  36. 42. Turner Syndrome <ul><li>• XO </li></ul><ul><li>phenotype-female </li></ul><ul><li>small functioning ovaries </li></ul><ul><li>short </li></ul><ul><li>no breast development </li></ul>
  37. 43. Down Syndrome <ul><li>Extra chromosome at the 21 st position </li></ul><ul><li>Enlarged tongues </li></ul><ul><li>Small, round ears </li></ul><ul><li>Heart defects </li></ul><ul><li>Stubby fingers and toes </li></ul><ul><li>Mental retardation </li></ul>
  38. 44. Klineflelter Syndrome <ul><li>XXY at 23 rd position </li></ul><ul><li>small testes, no sperm development </li></ul><ul><li>enlarged breast development </li></ul><ul><li>tall stature </li></ul>
  39. 45. Cri-du-chat <ul><li>Partial deletion from chromosome # 5 </li></ul><ul><li>Baby’s cry sounds like a cat </li></ul><ul><li>Severe mental retardation </li></ul><ul><li>Multiple anatomical malformations </li></ul>
  40. 46. Sex-linked Disorders
  41. 47. Hemophilia <ul><li>mental retardation </li></ul><ul><li>enlarged liver </li></ul><ul><li>flat broad nose, large tongue </li></ul>• inability to clot blood properly • bruise easily • many patients have been infected with AIDS Hunters Syndrome
  42. 48. Autosomal Dominate Disorders
  43. 49. Neurofibromatosis <ul><li>• Disorder of connective tissue </li></ul><ul><li>Affects bone, eyes, heart and blood vessels </li></ul><ul><li>Long legs and hands </li></ul><ul><li>Blood vessels lack elasticity </li></ul><ul><li>Can be slight to severe </li></ul><ul><li>Tumors on head, neck, and spine </li></ul>Marfan Syndrome
  44. 50. Huntington Disease <ul><li>Progressive degeneration of brain cortex </li></ul><ul><li>Symptoms begin around the age of 30-50 </li></ul><ul><li>Symptoms include </li></ul><ul><ul><ul><li>depression </li></ul></ul></ul><ul><ul><ul><li>forgetfulness </li></ul></ul></ul><ul><ul><ul><li>clumsiness </li></ul></ul></ul><ul><ul><ul><li>twitching </li></ul></ul></ul><ul><ul><ul><li>mood swings </li></ul></ul></ul>
  45. 51. Autosomal Recessive Disorders
  46. 52. Porphyria <ul><li>Prophyrin build-up(molecules formed during the synthesis of hemoglobin) </li></ul><ul><li>“ werewolf” </li></ul><ul><li>emotionally unstable </li></ul><ul><li>sensitive to light </li></ul><ul><li>self mutilation </li></ul>
  47. 53. Cystic Fibrosis <ul><li>very common, 40% of population are carriers </li></ul><ul><li>disease of exocrine glands, build up of thick mucus in the lungs that makes breathing difficult </li></ul><ul><li>causes respiratory infections </li></ul>
  48. 54. Leprechanism <ul><li>Short, elf-like appearance </li></ul><ul><li>Hypoglycemia </li></ul><ul><li>Progeria </li></ul><ul><li>Premature aging </li></ul><ul><li>Die of artery disease at age 10-15 </li></ul>