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a short introduction before taking genetics

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  1. 1. GeneticsGeneticsGenetics
  2. 2. What is Genetics ? Genetics is the study of heredity and variation Examples of genetic variation 1. Domesticated species 2. Human genetics 3. Natural Populations
  3. 3. History of Genetics •Domestication of animals •Cultivation of plants
  4. 4. Cultivated varieties
  5. 5. Animal Breeds
  6. 6. Human Genetic Variation
  7. 7. Variance
  8. 8. Which suspect matches the blood stain ? Bloodstain
  9. 9. Ethical Issues Boot GM out of animal feed
  10. 10. Cloning
  11. 11. Genetic JournalsGenetic Journals • American Journal of Medical Genetics Clinical Genetics • Developmental Genetics Human Molecular Genetics • Genetics European J. of Human Genetics • Genetics Selection Evolution Nature Genetics • Genetika Fungal Genetics and Biology • Genome Cancer Genetics and Cytogenetics • Genomics American J. Human Genetics • Hereditas Opthalmic Genetics • Japanese Journal of Human Genetics Human Genetics • Journal of Heredity Current Genetics • Molecular Biology and Evolution Animal Genetics • Molecular Ecology Brazilian J. Genetics • Molecular and General Genetics Biochemical Genetics • Theoretical and Applied Genetics J. of Medical Genetics • Trends in Genetics
  12. 12. Basic Concepts of Genetics Nucleus - contains genetic material DNA - genetic material 4 bases (nucleotides G, C, A, T) Gene - functional unit of heredity sequence of 4 nucleotides Chromosome -linear DNA molecule
  13. 13. Basic Concepts of Genetics Cell/nuclear division •Mitosis (somatic tissue): identical cells •Meiosis (germ tissue): gametes
  14. 14. Basic Concepts of Genetics •Mendelian Genetics (transmission genetics) •Molecular Genetics (hereditary material)
  15. 15. Historical Notes 1865 Gregor Mendel - controlled genetic experiments (garden peas) - statistical regularity - theory of inheritance
  16. 16. Understanding Genetics • Relationship between: GENOTYPE ENVIRONMENT PHENOTYPE set of genes morphology inherited physiology behaviour
  17. 17. Mendelian Genetics Requirements: 1. Attributes of the phenotype that vary among individuals 2. Phenotypic variation caused by genetic differences
  18. 18. Genotype and Phenotype • The genotype is our actual genes. We cannot see our genes. • The phenotype is the physical expression of those genes.
  19. 19. • Genes - cannot be observed directly • Phenotypes - observed directly ** inheritance of phenotypes used to infer the inheritance of genes Mendelian Genetics
  20. 20. Mendel’s Experiments Seven Pea varieties “True Breeding Lines” Character “traits” Phenotypes 1. seed shape round, wrinkled 2. seed colour yellow, green 3. flowers (pods) axial, terminal 4. pods full, constricted 5. pods yellow, green 6. flowers violet, white 7. stem tall, dwarf
  21. 21. Fertilization Gametes carry the genetic information about an organism. The male gamete produce Sperm. The female gametes produce Eggs. The process in which one gamete is united with another is called Fertilization.
  22. 22. Fertilization Mommy DaddyDaddy BABYBABY
  23. 23. Self-Fertilization • When an organism has both male and female gametes, they are able to self- fertilize.
  24. 24. Advantages • easy to grow • matures in a season • self-fertilizing • easy to cross-fertilize
  25. 25. Dominance • Some characteristics overshadow others when crossed. • This is referred to as a Dominant trait. • The unseen trait is said to be Recessive. • Dominant traits are represented on charts by a capital letter. • Recessive traits are represented by a lower case letter
  26. 26. Pure Lines (Homozygous) • When an organism is said to be of pure lines, it means their genotype is two identical alleles. • TT is the pure line for a tall plant. • tt is the pure line for a short plant.
  27. 27. Hybrids (Heterozygous) • When parents of two different pure lines are crossed, the offspring are called hybrids. • A hybrid’s genotype consists of two different alleles. • The genotype Tt would be a tall plant hybrid.
  28. 28. Homozygous and Heterozygous • When an organism has identical alleles, it is said to be homozygous. • TT, and tt would both be homozygous • When an organism has two different alleles, it is heterozygous. • Tt is heterozygous.
  29. 29. Punnett Square T T T T TT TT TT TT
  30. 30. Cross Pollination
  31. 31. Punnett Square of Cross Pollination T t T T TT TT Tt Tt MOM DAD
  32. 32. Punnett SquarePunnett Square (Monohybrid Cross)(Monohybrid Cross) T t T t TT Tt Tt tt MOM DAD
  33. 33. Punnett SquarePunnett Square T t t t Tt Tt tt tt MOM DAD
  34. 34. Punnett SquarePunnett Square t t t t tt tt tt tt MOM DAD
  35. 35. Mendel’s Experimental Approach Suitable experimental organism • examine few traits in each experiment • accurate quantitative records • analyzed data formulated hypotheses
  36. 36. Genetic Analysis (pea shape)
  37. 37. Hypothesis to explain results 1. Hereditary determinants (genes) 2. Each adult plant has a gene pair F1 plants: one gene dominant phenotype one gene recessive phenotype
  38. 38. Hypothesis (continued) 3. Members of a gene pair segregate equally into the gametes 4. Each gamete has only one member of a gene pair 5. Gametes combine at random to form zygote
  39. 39. Hypothesis
  40. 40. Self Fertilization
  41. 41. Test of Equal Segregation Hypothesis
  42. 42. Three parts: 1. Hereditary characteristics are determined by distinct units or factors. 2. For each characteristic, an individual carries two factors, one inherited from each parent. 3. The two factors of each pair segregate from each other and end up in separate gametes. Principle of Segregation
  43. 43. If a plant is short, what is its genotype? • It must be homozygous recessive, tt.
  44. 44. If a plant is tall, what is its genotype? • It could be homozygous dominant, or heterozygous. TT, or Tt. • To determine which genotype it is we use a test cross.
  45. 45. Test Cross T t t t Tt Tt tt tt Heterozygous Known homozygous recessive 1/2 Tall 1/2 Short
  46. 46. Test Cross T T t t Tt Tt Tt Tt Homozygous Known homozygous recessive All Tall N0 Short
  47. 47. Genetic Terminology Genes: hereditary elements • Alleles: forms of a gene: A a • Heterozygote: Aa • Homozygotes: AA aa • Genotype: Genetic makeup • Phenotype: What we actually see • Dominance AA, Aa same phenotype
  48. 48. Summary Experimental: 1. Two pure breeding lines 2. Cross --------> F1 hybrid 3. Self F1 ------> F2
  49. 49. Summary Results: 1. F1 one phenotype 2. F2 3:1 ratio of 2 phenotypes
  50. 50. Summary Inference: 1. Single major gene 2. dominant phenotype 3. equal segregation 4. existence of genes inferred