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Mendelian Inheritance

Mendelian Inheritance

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Mendelian Inheritance

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  1. Mendelian Inheritance BIO 2215 Oklahoma City Community College Dennis Anderson

  2. Gregor Mendel • Father of Genetics • 1823-1884 • Monk in Austria • Experimented with garden peas

  3. Tall Tall Short

  4. Mendel’s Hypotheses • Each parent has two factors (alleles) • Each parent gives one of those factors to the offspring • Tall has TT • Short has tt • Tall is dominant • Short is recessive

  5. T t Tt TT tt

  6. T T TT TT TT

  7. t t tt tt tt

  8. Law of Segregation • Alleles separate during gamete production • Gametes have one allele for each trait • During fertilization gametes combine at random to form individuals of the next generation

  9. Discovery of Chromosomes in 1900 Confirmed Law of Segregation • Chromosomes are in pairs • Each chromosome has one of the allele pair

  10. Meiosis Metaphase Chromosomes line up in a double row. T T t t Assume a T allele on each red chromatid and a t allele on each blue chromatid

  11. Chromosomes separate Each each daughter cell gets doubled chromosomes t t T T

  12. Doubled Chromosomes Separate in Second Meiotic Division T T t t

  13. Each gamete will have a T allele or a t allele T T t t

  14. Allele • Member of a paired gene • One allele comes from each parent • Represented by a single letter

  15. Dominant & Recessive Alleles • Dominant alleles are expressed • Recessive alleles are not expressed in the presence of a dominant allele • Recessive alleles are only expressed if both recessive alleles are present

  16. Gene • A unit of heredity that controls the development of one trait • Made of DNA • Most genes are composed of two alleles

  17. Homozygous • Both alleles alike • AA or aa

  18. Heterozygous • Alleles are different • Aa

  19. Genotype • Genetic make up • Represented by alleles • TT & Tt are genotypes for tall pea plants

  20. Phenotype • A trait • Genotype determines the phenotype • Tall is a phenotype

  21. Homologous Chromosomes • Chromosomes of the same pair • Each homologue will have one allele for a paired gene • Homologous chromosomes pair up during meiosis • Only one of each homologue will be in each gamete

  22. Sickle Cell Anemia • RBCs sickle shaped • Anemia • Pain • Stroke • Leg ulcers • Jaundice • Gall stones • Spleen, kidney & lungs

  23. Sickle Cell Anemia • Recessive allele s, codes for hemoglobin S • Long rod-like molecules • Stretches RBC into sickle shape • Homozygous recessive ss, have sickle cell anemia • Heterozygous Ss, are carriers

  24. Albinism • Lack of pigment • Skin • Hair • Eyes

  25. a A AA = Normal pigmentation Aa = Normal pigmentation aa = Albino Enzyme Amino Acids Melanin Pigment

  26. PKU Disease • Phenylalanine excess • Mental retardation if untreated

  27. p P PP = Normal Pp = Normal pp = PKU Enzyme Phenylalanine Tyrosine

  28. Monohybrid Cross or One Trait A man & woman are both carriers (heterozygous) for albinism. What is the chance their children will inherit albinism?

  29. AA = Normal pigmentation Aa = Normal pigmentation (carrier) aa = Albino A A a a Man = Aa Woman = Aa

  30. A A a a Aa AA Aa aa

  31. Aa AA Aa aa Genotypes 1 AA, 2Aa, 1aa Phenotypes 3 Normal 1 Abino Probability 25% for albinism

  32. A man & woman are both carriers (heterozygous) for PKU disease. What is the chance their children will inherit PKU disease?

  33. PP = Normal Pp = Normal (carrier) pp = PKU disease Pp PP Pp pp P p P p

  34. Pp PP Pp pp Genotypes 1 PP, 2Pp, 1pp Phenotypes 3 Normal 1 PKU disease Probability 25% for PKU disease

  35. A man with sickle cell anemia marries a woman who is a carrier. What is the chance their children will inherit sickle cell anemia?

  36. SS = Normal Ss = Normal (carrier) ss = Sickle Cell ss Ss Ss ss S s s s

  37. ss Ss Ss ss Genotypes 2 Ss, 2ss Phenotypes 2 Normal (carriers) 2 Sickle cell Probability 50% for Sickle cell

  38. Dwarfism Dwarfism = D Normal height = d DD = Dwarfism Dd = Dwarfism dd = Normal height Dwarf Band

  39. A man with heterozygous dwarfism marries a woman who has normal height. What is the chance their children will inherit dwarfism? Dwarfism is dominant.

  40. DD = Dwarf Dd = Dwarf dd = Normal Dd Dd dd dd d d D d

  41. Dd Dd dd dd Genotypes 2 Dd, 2dd Phenotypes 2 Normal 2 Dwarfs Probability 50% for Dwarfism

  42. Law of Independent Assortment • The inheritance of one gene does not influence the inheritance of another gene if they are on separate chromosomes. • The gene for albinism does not affect the gene for dwarfism

  43. Dihybrid Cross or Two Traits • A heterozygous tall plant that is also heterozygous for yellow seeds is crossed with another plant with the same genotype • Tall and yellow seeds are dominant to short and green seeds.

  44. TY Ty tY ty What gametes can each parent produce? Tall Yellow Tall Yellow TtYy TtYy TY Ty tY ty

  45. TY Ty tY ty 9 Tall-Yellow TY TTYY TTYy TtYY TtYy 3 Tall-Green Ty TTYy TTyy TtYy Ttyy TtYY TtYy ttYY ttYy tY 3 Short-Yellow TtYy ty Ttyy ttYy ttyy Match gametes on a Punnent Square 1 Short-Green

  46. A man with blue eyes and normal height marries a woman with heterozygous brown eyes and heterozygous dwarfism. What are the possible phenotypes of their children? Dwarfism & brown eyes are dominant.

  47. DB Db dB db What gametes can each parent produce? Normal height-Blue Dwarf-Brown ddbb DdBb db

  48. DdBb Dwarf-Brown eyes DB Ddbb Dwarf-blue eyes Db dB ddBb Normal height-Brown eyes Normal height-Blue eyes db ddbb Match gametes on Punnent Square db

  49. The End