Mendelian Inheritance

Chp. 4 pg 75 – 94

  1. Gregor Mendel- “father of genetics”
  2. History
  3. Priest at a monastery
  4. Also taught and did research in natural science
  5. Such a good substitute teacher that they sent him to get his bachelors degree at age 29 where he learned the statistics he used in genetics
  6. Crossed and catalogued more than 24,034 plants
  7. Mendel’s Experiments-
  8. Single traits that have 2 expressions
  9. height – “short” or “tall”
  10. “true breeding”- short crossed with short produced short plants
  11. “tall “ crossed with “short” tallness seemed to mask shortness
  12. The trait that tends to mask the other is said to be dominant
  13. The masked trait is said to be recessive.
  14. Monohybrid cross-
  15. Crossing individuals who are heterozygous for a trait
  16. Short plants that had arisen from crossing the hybrid tall plants
  17. Law of Segregation- The distribution of alleles of a gene into separate gametes during meiosis (Mendel’s 1st law)
  18. Genes
  19. Homozygous- an individual has 2 identical alleles for a gene
  20. Heterozygous- an individual with 2 different alleles.
  21. Homozygous recessive- uu
  22. Homozygous dominant – UU
  23. Heterozygous- Uu
  24. Genotype- the organisms alleles
  25. Phenotype- the organisms expression of the alleles or appearance
  26. Wild Type- most common expression of a particular allele combination in a population
  27. Mutant- a variant of a gene’s expression that arises when the gene undergoes a change or mutation
  28. Analyzing genetic crosses
  29. First generation - P1
  30. Second generation – F1
  31. Third generation – F2
  32. Tool we use is a Punnett Square
  33. Single gene inheritance
  34. Called Mendelian, Unifactorial or single-gene inheritance
  35. Mendelian conditions are extremely rare
  36. Modes of Inheritance (Autosome- non-sex determining chromosome)
  37. Autosomal Dominant Inheritance-
  38. either sex,
  39. if child has trait at least one parent must have the trait.
  40. Do not skip generations. If children do not have the trait they can not pass it on.
  41. Autosomal Recessive Inheritance-
  42. either sex
  43. affected individuals have homozygous recessive genotype
  44. both parents must carry the trait
  45. may skip generations because offspring can be carriers
  46. Inheritance of 2 genes- Independent Assortment
  47. Law of Independent Assortment (Mendel’s 2nd Law)- The inheritance of one gene does not influence the chance of inheriting the other
  48. Mendel’s Experiments-
  49. Traits- seed shape (R gene) and seed color (Y gene)
  50. Crossed “true breeding” round, yellow plants with “true breeding” wrinkled, green plants and all progeny had round yellow seeds
  51. These offspring where double heterozygotes (RrYy)
  52. Round is dominant to wrinkled, Yellow dominant to green
  53. Use a Dihybrid Cross- (Fig. 4.10) a cross of individuals who are heterozygous for two traits
  54. Pedigree Analysis- (Fig. 4.13 – legend of symbols and examples)
  55. Pedigree- Charts used to display family relationships and to follow which relatives have specific phenotypes and sometimes genotypes.