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CH-11

CH-11. MENDELIAN PATTERNS OF INHERITANCE. 11.1 Gregor MENDEL. – FATHER of Genetics – 1860s Laws of Heredity 1 - Each trait controlled by 2 alleles – Particulate Theory 2 - Alleles on homologous chromosomes at a specific site – gene locus. Gregor Mendel. Austrian monk

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CH-11

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  1. CH-11 • MENDELIAN PATTERNS OF INHERITANCE CH-11(8) Mendelian Patterns of Inheritance

  2. 11.1 Gregor MENDEL – FATHER of Genetics – 1860s • Laws of Heredity • 1 - Each trait controlled by 2 alleles – Particulate Theory • 2 - Alleles on homologous chromosomes at a specific site – gene locus. CH-11(8) Mendelian Patterns of Inheritance

  3. Gregor Mendel • Austrian monk Breeding experiments with the garden pea. Gathered and documented mathematical data from his experiments • Formulated fundamental laws of heredity in early 1860s. CH-11(8) Mendelian Patterns of Inheritance

  4. Blending Concept – Before Mendel • Both sexes contribute equally • But parents of contrasting appearance produce offspring of intermediate appearance CH-11(8) Mendelian Patterns of Inheritance

  5. TERMS • Alleles – alternative forms of a gene – occur at the same locus on homologous • Dominant allele – masks the expression of recessive alleles • Recessive allele – expressed only in the homo-rec form • Homozygous – • Both alleles are either dominant or recessive • Heterozygous – • Alleles are different – one dominant. one recessive CH-11(8) Mendelian Patterns of Inheritance

  6. A A A A y y Y Y Alleles CH-11(8) Mendelian Patterns of Inheritance

  7. Genotype– • refers to the alleles an organism receives at fertilization. • HOMOZYGOUS DOMINANT • RECESSIVE. • HETEROZYGOUS CH-11(8) Mendelian Patterns of Inheritance

  8. PHENOTYPE • PHYSICAL APPEARANCE OF THE ORGANISM. • THE EXPRESSION OF THE ALLELE. CH-11(8) Mendelian Patterns of Inheritance

  9. Mendel’s Experiments Garden Pea – – True breeders offspring like parents and each other • True breeders – yield homozygous offspring. • Trait is always expressed. CH-11(8) Mendelian Patterns of Inheritance

  10. Garden Pea TraitsStudied by Mendel CH-11(8) Mendelian Patterns of Inheritance

  11. 11.2 ONE TRAIT INHERITANCE • Cross Pollination between two strains • P-Generation original parents • F1 – first generation of Offspring • Tall Plants x Short Plants • Short plants pollinated Tall Plants • F1 generation – ALL TALL • F1 PLANTS SELF-POLLINATED • ¾ Tall ¼ short • 3:1 ratio CH-11(8) Mendelian Patterns of Inheritance

  12. One-Trait Test CrossUnknown is Homozygous Dominant CH-11(8) Mendelian Patterns of Inheritance

  13. LAW 1 – LAW OF SEGREGATION • EACH ORGANISM W/ 2 FACTORS FOR EACH TRAIT • FACTORS SEPARATE DURING MEIOSIS SO EACH GAMETE CONTAINS ONLY ONE FACTOR CH-11(8) Mendelian Patterns of Inheritance

  14. 11.2c MONOHYBRID GENETICS PROBLEMS: • To solve these: • Which characteristic is dominant • Must determine Genotype of both parents • Crossing a dominant phenotype with a recessive phenotype indicates the genotype of the dominant phenotype CH-11(8) Mendelian Patterns of Inheritance

  15. Used to figure out probable results of a genetic cross. Tall vs short PUNNETT SQUARE FOIL method CH-11(8) Mendelian Patterns of Inheritance

  16. LAWS OF PROBABILITY • Chance has no memory • Flipping a coin… • Chance of H = 0.5 Chance of T = 0.5 CH-11(8) Mendelian Patterns of Inheritance

  17. Multiplicative Law – The chance of 2 or more independent events occurring together is the PRODUCT of their chance of occurring Separately. Genotype = Aa crossed with Aa Chance of A = 0.5. chance of a = 0.5 CH-11(8) Mendelian Patterns of Inheritance

  18. ADDITIVE Law- to determine Phenotypes • – chance that event can occur in 2 or more different ways is SUM of individual chances. chance of getting specific PHENOTYPE is sum of chances of getting all the right genotypes CH-11(8) Mendelian Patterns of Inheritance

  19. Dihybrid cross: Dihybrids are the PRODUCT of two different strains that differ in regard to two traits CH-11(8) Mendelian Patterns of Inheritance

  20. 11.3TWO-TRAIT Inheritance • 2nd series of Crosses • Crossed True breeders differing in two traits • Tall green X short yellow • If so then only 2 Phenotypes. Tall Green and Short/Yellow would occur. CH-11(8) Mendelian Patterns of Inheritance

  21. Instead ALL Four phenotypes occurred • tall green short green • tall yellow short yellow CH-11(8) Mendelian Patterns of Inheritance

  22. MENDEL’s 2nd LAW of Inheritance • LAW of INDEPENDENT ASSORTMENT. • Members of one pair of factors separate independently of members of another pair of factors. All possible combinations of factors can occur. CH-11(8) Mendelian Patterns of Inheritance

  23. Dihybrid Cross • (parents differ in TWO traits) • Cross a HOMOZYGOUS DOMINANT with a HOMOZYGOUS RECCESSIVE • Tall green TTGG v short yellow ttgg • TG and tg = TtGg CH-11(8) Mendelian Patterns of Inheritance

  24. Dihybrid cross • F1 Generation is TtGg = heterozygous for two traits. (4 possible gametes) • Then cross that and f2 generation yields an CH-11(8) Mendelian Patterns of Inheritance

  25. 2-Trait Test cross • Is individual w/ dominant traits homozygous or heterozygous for either of the 2 traits. • cross a dom pheno with a rec. pheno • Is a test cross necessary for determining the genotype of a homozygous recessive individual? CH-11(8) Mendelian Patterns of Inheritance

  26. 11.4 human genetic disorders • inherited alleles • autosomal chromosomes – somatic cells – non-sex cells. • Pedigree chart – to determine if condition is dom. or rec. CH-11(8) Mendelian Patterns of Inheritance

  27. Pedigree Charts autosomal recessive char. autosomal dominant char. patterns of inheritance CH-11(8) Mendelian Patterns of Inheritance

  28. Autosomes: • non-sex chromosomes same between sexes. CH-11(8) Mendelian Patterns of Inheritance

  29. Autosomal Recessive Pedigree Chart CH-11(8) Mendelian Patterns of Inheritance

  30. AUTOSOMAL RECESSIVE DISORDERS • TAY-SACHS DISEASE • CYSTIC FIBROSIS • PHENYLKETONURIA CH-11(8) Mendelian Patterns of Inheritance

  31. AUTOSOMAL DOMINANT DISORDERS • Children can get it if only one parent is affected • Heterozygotes are affected • Affected parents can have normal offspring • unaffected parents will have unaffected children • males and females w/ equal chances. CH-11(8) Mendelian Patterns of Inheritance

  32. Autosomal Dominant Pedigree Chart CH-11(8) Mendelian Patterns of Inheritance

  33. ASDs • NEUROFIBROMATOSIS • HUNTINGTON DISEASE CH-11(8) Mendelian Patterns of Inheritance

  34. INCOMPLETE DOMINANCE • red v white flower = pink • protein missing or inactive • wavy hair - curly & straight parents • sickle cell disease CH-11(8) Mendelian Patterns of Inheritance

  35. PLEIOTROPY: • SOME GENES MAY AFFECT MORE THAN ONE CHARACTERISTIC • ALLELE LINKED TO TWO OR MORE CHARACTERS • MARFAN SYNDROME –TALL. THIN PERSON W/ LONG THIN FINGERS AND OTHER PROBLEMS. CH-11(8) Mendelian Patterns of Inheritance

  36. MULTIPLE ALLELES • Several forms of a gene control a trait • ABO blood types (codominance) • More than one allele is fully expressed. • Ia = A antigen on rbc • Ib = B • ii = no antigens CH-11(8) Mendelian Patterns of Inheritance

  37. CO-DOMINANCE: • BOTH ALLELES ARE FULLY EXPRESSED • BLOOD TYPE • AB – BLOOD ALLELES PRODUCE SPECIFIC SET OF GLYCOPROTEINS • A – ALLELES produce different glycoproteins • B – ALLELES produce another set of glycoproteins.. CH-11(8) Mendelian Patterns of Inheritance

  38. Inheritance of Blood Type CH-11(8) Mendelian Patterns of Inheritance

  39. MULTIPLE ALLELES: • More than one pair of alleles may be REQUIRED. • PEPPERED MOTH. • 3 sets of color-coding genes. • m M’ and M • MM. MM’. Mm  dark moth • M’M’ and M’m  lighter moth • mm  lightest moth CH-11(8) Mendelian Patterns of Inheritance

  40. POLYGENIC INHERITANCE • one trait governed by several genes • For example: • Seed color in wheat • Height in humans • Skin color in humans CH-11(8) Mendelian Patterns of Inheritance

  41. Height in Human Beings CH-11(8) Mendelian Patterns of Inheritance

  42. ENVIRONMENT PLAYS ROLE • Affects phenotype. • Some genes modify the effects of others. • Two more genes can control one trait • Dominance can occur in degrees CH-11(8) Mendelian Patterns of Inheritance

  43. ENVIRONMENTAL EFFECTS: • Temperature: • HIMALAYAN RABBITS CH-11(8) Mendelian Patterns of Inheritance

  44. EPISTASIS • Gene at one place on chromosome INTERFERS with the EXPRESSION (Phenotypic) of gene at another locus. Example: Sweet Peas • 2 gene pairs affect color. and HOMO REC of either pair results in lack of color. • Genes at two different loci interact to control a single trait. CH-11(8) Mendelian Patterns of Inheritance

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