Mendelelian Genetics   copyright cmassengale   1
Gregor Mendel (1822-1884)   Responsible  for the Laws    governing Inheritance of     Traits                  copyright cm...
Gregor Johann Mendel   Austrian monk   Studied theinheritance oftraits in pea plants  Developed thelaws of inheritance...
Gregor Johann Mendel  Between 1856and 1863, Mendelcultivated andtested some 28,000pea plants  He found thatthe plantsoff...
Site of                        Gregor                        Mendel’s                        experimental                 ...
Particulate Inheritance  Mendel stated thatphysical traits areinherited as “particles”  Mendel did notknow that the“part...
Genetic TerminologyTrait - any characteristicthat can be passed from parentto offspringHeredity - passing of traitsfrom ...
Types of Genetic Crosses Monohybrid cross - crossinvolving a single traite.g. flower color Dihybrid cross - crossinvolvi...
Punnett SquareUsed to helpsolve geneticsproblems                 copyright cmassengale   9
copyright cmassengale   10
Designer “Genes” Alleles - two forms of a gene(dominant & recessive) Dominant - stronger of two genesexpressed in the hy...
More TerminologyGenotype - gene combinationfor a trait (e.g. RR, Rr, rr)Phenotype - the physicalfeature resulting from a...
Genotype & Phenotype in FlowersGenotype of alleles:R = red flowerr = yellow flowerAll genes occur in pairs, so 2alleles af...
GenotypesHomozygous genotype - genecombination involving 2 dominantor 2 recessive genes (e.g. RR orrr); also called pure ...
Genes and EnvironmentDetermine Characteristics          copyright cmassengale   15
Mendel’s Pea Plant  Experiments        copyright cmassengale   16
Why peas, Pisum sativum?  Can be grown ina small area  Produce lots ofoffspring  Produce pureplants when allowedto self...
Reproduction in Flowering PlantsPollen contains sperm   Produced by the   stamenOvary contains eggs   Found inside the   f...
Mendel’s Experimental             MethodsMendel hand-pollinatedflowers using a paintbrush   He could snip the   stamens to...
How Mendel BeganMendelproducedpurestrains byallowing theplants toself-pollinatefor severalgenerations               copyri...
Eight Pea Plant TraitsSeed shape --- Round (R) or Wrinkled (r)Seed Color ---- Yellow (Y) or  Green (y )Pod Shape --- Smoot...
copyright cmassengale   22
copyright cmassengale   23
Mendel’s Experimental Results             copyright cmassengale   24
Did the observed ratio match    the theoretical ratio?The theoretical or expected ratio ofplants producing round or wrinkl...
Generation “Gap”Parental P1 Generation = the parental  generation in a breeding experiment.F1 generation = the first-gener...
Following the GenerationsCross 2   Results Cross 2 Hybrids  Pure     in all        get Plants   Hybrids 3 Tall & 1 ShortTT...
Monohybrid Crosses    copyright cmassengale   28
P1 Monohybrid CrossTrait: Seed ShapeAlleles: R – Round r – WrinkledCross: Round seeds    x Wrinkled seeds                R...
P1 Monohybrid Cross ReviewHomozygous dominant xHomozygous recessiveOffspring all Heterozygous(hybrids)Offspring called ...
F1 Monohybrid CrossTrait: Seed ShapeAlleles: R – Round r – WrinkledCross: Round seeds    x Round seeds                Rr  ...
F1 Monohybrid Cross Review Heterozygous x heterozygous Offspring:25% Homozygous dominant RR50% Heterozygous Rr25% Homozy...
What Do the Peas Look Like?           copyright cmassengale   33
…And Now the Test CrossMendel then crossed a pure & a hybrid from his F2 generationThis is known as an F2 or test crossThe...
F2 Monohybrid Cross (1st)Trait: Seed ShapeAlleles: R – Round r – WrinkledCross: Round seeds    x Round seeds              ...
F2 Monohybrid Cross (2nd)Trait: Seed ShapeAlleles: R – Round r – WrinkledCross: Wrinkled seeds x Round seeds              ...
F2 Monohybrid Cross ReviewHomozygous xheterozygous(hybrid)Offspring:50% Homozygous RR or rr50% Heterozygous Rr Phenoty...
Practice Your CrossesWork the P1, F1, and both F2  Crosses for each of the   other Seven Pea Plant           Traits       ...
Mendel’s Laws     copyright cmassengale   39
Results of Monohybrid CrossesInheritable factors or genes are responsible for all heritable characteristicsPhenotype is ba...
Law of DominanceIn a cross of parents that arepure for contrasting traits, onlyone form of the trait will appear inthe nex...
Law of Dominance       copyright cmassengale   42
Law of SegregationDuring the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from e...
Applying the Law of Segregation            copyright cmassengale   44
Law of Independent         AssortmentAlleles for different traits are distributed to sex cells (& offspring) independently...
Dihybrid CrossA breeding experiment that tracks the inheritance of two traits.Mendel’s “Law of Independent Assortment”a. E...
Question: How many gametes will be producedfor the following allele arrangements? Remember: 2n (n = # of heterozygotes)   ...
Answer:1. RrYy: 2n = 22 = 4 gametes    RY   Ry   rY ry2. AaBbCCDd: 2n     = 23 =                8 gametes   ABCD ABCd     ...
Dihybrid CrossTraits: Seed shape & Seed colorAlleles: R round         r wrinkled         Y yellow         y green         ...
Dihybrid Cross      RY   Ry               rY          ryRYRyrYry                copyright cmassengale        50
Dihybrid Cross    RY    Ry      rY           ryRY RRYY                                         Round/Yellow:     9        ...
Dihybrid Cross                             Round/Yellow: 9                             Round/green:     3                 ...
Test CrossA mating between an individual of unknown  genotype and a homozygous recessive  individual.Example: bbC__ x bbcc...
Test CrossPossible results:     bC     b___              C                              bC     b___                       ...
Summary of Mendel’s laws                PARENT   LAW                                            OFFSPRING                 ...
Incomplete Dominance         and    Codominance        copyright cmassengale   56
Incomplete DominanceF1 hybrids have an appearance somewhat  in between the phenotypes of the two  parental varieties.Examp...
Incomplete Dominance   r   r                          produces theR Rr   Rr                          F1 generationR Rr   R...
Incomplete Dominance         copyright cmassengale   59
CodominanceTwo alleles are expressed (multiple alleles) in heterozygous individuals.Example: blood type 1.   type   A    =...
Codominance ProblemExample: homozygous male Type B (IBIB)                     x      heterozygous female Type A (IAi)     ...
Another Codominance Problem• Example: male Type O (ii)                 x          female type AB (IAIB)               IA  ...
CodominanceQuestion: If a boy has a blood type O and       his sister has blood type AB,       what are the genotypes and ...
CodominanceAnswer:    IA    iIB IAIB        Parents:               genotypes = IAi and IBi               phenotypes = A an...
Sex-linked TraitsTraits (genes) located on the sex chromosomesSex chromosomes are X and YXX genotype for femalesXY genotyp...
Sex-linked Traits Example: Eye color in fruit flies                 Sex Chromosomes                         fruit fly     ...
Sex-linked Trait ProblemExample: Eye color in fruit flies  (red-eyed male) x (white-eyed female)      XRY           x     ...
Sex-linked Trait Solution:      Xr        Xr                                   50% red eyedXR X X X X     R     r    R    ...
Female Carriers     copyright cmassengale   69
Genetic Practice   Problems      copyright cmassengale   70
Breed the P1 generationtall (TT) x dwarf (tt) pea plants             t          t         T         T                 copy...
Solution:tall (TT) vs. dwarf (tt) pea plants    t    t    Tt   Tt           produces theT                      F1 generati...
Breed the F1 generationtall (Tt) vs. tall (Tt) pea plants             T            t         T         t                 c...
Solution:    tall (Tt) x tall (Tt) pea plants       T      t                                           produces the      T...
copyright cmassengale   75
Upcoming SlideShare
Loading in …5
×

Mendelian Genetics

736 views

Published on

Published in: Education, Lifestyle, Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
736
On SlideShare
0
From Embeds
0
Number of Embeds
2
Actions
Shares
0
Downloads
64
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13 Fig. 5.co
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics 04/08/13
  • Mendelian Genetics

    1. 1. Mendelelian Genetics copyright cmassengale 1
    2. 2. Gregor Mendel (1822-1884) Responsible for the Laws governing Inheritance of Traits copyright cmassengale 2
    3. 3. Gregor Johann Mendel Austrian monk Studied theinheritance oftraits in pea plants Developed thelaws of inheritance Mendels workwas not recognizeduntil the turn ofthe 20th century copyright cmassengale 3
    4. 4. Gregor Johann Mendel Between 1856and 1863, Mendelcultivated andtested some 28,000pea plants He found thatthe plantsoffspring retainedtraits of theparents Called the“Father of copyright cmassengale 4
    5. 5. Site of Gregor Mendel’s experimental garden in the Czech Republiccopyright cmassengale 5
    6. 6. Particulate Inheritance Mendel stated thatphysical traits areinherited as “particles” Mendel did notknow that the“particles” wereactually Chromosomes& DNA copyright cmassengale 6
    7. 7. Genetic TerminologyTrait - any characteristicthat can be passed from parentto offspringHeredity - passing of traitsfrom parent to offspringGenetics - study of heredity copyright cmassengale 7
    8. 8. Types of Genetic Crosses Monohybrid cross - crossinvolving a single traite.g. flower color Dihybrid cross - crossinvolving two traitse.g. flower color & plant height copyright cmassengale 8
    9. 9. Punnett SquareUsed to helpsolve geneticsproblems copyright cmassengale 9
    10. 10. copyright cmassengale 10
    11. 11. Designer “Genes” Alleles - two forms of a gene(dominant & recessive) Dominant - stronger of two genesexpressed in the hybrid;represented by a capital letter (R) Recessive - gene that shows upless often in a cross; representedby a lowercase letter (r) copyright cmassengale 11
    12. 12. More TerminologyGenotype - gene combinationfor a trait (e.g. RR, Rr, rr)Phenotype - the physicalfeature resulting from agenotype (e.g. red, white) copyright cmassengale 12
    13. 13. Genotype & Phenotype in FlowersGenotype of alleles:R = red flowerr = yellow flowerAll genes occur in pairs, so 2alleles affect a characteristicPossible combinations are:Genotypes RR Rr rrPhenotypes RED RED YELLOW copyright cmassengale 13
    14. 14. GenotypesHomozygous genotype - genecombination involving 2 dominantor 2 recessive genes (e.g. RR orrr); also called pure Heterozygous genotype - genecombination of one dominant &one recessive allele    (e.g. Rr);also called hybrid copyright cmassengale 14
    15. 15. Genes and EnvironmentDetermine Characteristics copyright cmassengale 15
    16. 16. Mendel’s Pea Plant Experiments copyright cmassengale 16
    17. 17. Why peas, Pisum sativum? Can be grown ina small area Produce lots ofoffspring Produce pureplants when allowedto self-pollinateseveral generations Can beartificially cross-pollinated copyright cmassengale 17
    18. 18. Reproduction in Flowering PlantsPollen contains sperm Produced by the stamenOvary contains eggs Found inside the flower Pollen carries sperm to the eggs for fertilization Self-fertilization can occur in the same flower Cross-fertilization can occur between flowers copyright cmassengale 18
    19. 19. Mendel’s Experimental MethodsMendel hand-pollinatedflowers using a paintbrush He could snip the stamens to prevent self-pollination Covered each flower with a cloth bagHe traced traits throughthe several generations copyright cmassengale 19
    20. 20. How Mendel BeganMendelproducedpurestrains byallowing theplants toself-pollinatefor severalgenerations copyright cmassengale 20
    21. 21. Eight Pea Plant TraitsSeed shape --- Round (R) or Wrinkled (r)Seed Color ---- Yellow (Y) or  Green (y )Pod Shape --- Smooth (S) or wrinkled (s )Pod Color ---  Green (G) or Yellow (g)Seed Coat Color ---Gray (G) or White (g)Flower position---Axial (A) or Terminal (a)Plant Height --- Tall (T) or Short (t)Flower color --- Purple (P) or white (p ) copyright cmassengale 21
    22. 22. copyright cmassengale 22
    23. 23. copyright cmassengale 23
    24. 24. Mendel’s Experimental Results copyright cmassengale 24
    25. 25. Did the observed ratio match the theoretical ratio?The theoretical or expected ratio ofplants producing round or wrinkled seedsis 3 round :1 wrinkledMendel’s observed ratio was 2.96:1The discrepancy is due to statisticalerrorThe larger the sample the more nearlythe results approximate to thetheoretical ratio copyright cmassengale 25
    26. 26. Generation “Gap”Parental P1 Generation = the parental generation in a breeding experiment.F1 generation = the first-generation offspring in a breeding experiment. (1st filial generation) From breeding individuals from the P1 generationF2 generation = the second-generation offspring in a breeding experiment. (2nd filial generation) From breeding individuals from the F1 generation copyright cmassengale 26
    27. 27. Following the GenerationsCross 2 Results Cross 2 Hybrids Pure in all get Plants Hybrids 3 Tall & 1 ShortTT x tt Tt TT, Tt, tt copyright cmassengale 27
    28. 28. Monohybrid Crosses copyright cmassengale 28
    29. 29. P1 Monohybrid CrossTrait: Seed ShapeAlleles: R – Round r – WrinkledCross: Round seeds x Wrinkled seeds RR x rr Genotype: Rr r r Phenotype: Round Phenotype R Rr Rr Genotypic Ratio: All alike R Rr Rr Phenotypic Ratio: All alike copyright cmassengale 29
    30. 30. P1 Monohybrid Cross ReviewHomozygous dominant xHomozygous recessiveOffspring all Heterozygous(hybrids)Offspring called F1 generationGenotypic & Phenotypic ratio isALL ALIKE copyright cmassengale 30
    31. 31. F1 Monohybrid CrossTrait: Seed ShapeAlleles: R – Round r – WrinkledCross: Round seeds x Round seeds Rr x Rr Genotype: RR, Rr, rr R r Phenotype: Round & Phenotype RR Rr wrinkled R G.Ratio: 1:2:1 r Rr rr P.Ratio: 3:1 copyright cmassengale 31
    32. 32. F1 Monohybrid Cross Review Heterozygous x heterozygous Offspring:25% Homozygous dominant RR50% Heterozygous Rr25% Homozygous Recessive rr Offspring called F2 generation Genotypic ratio is 1:2:1Phenotypic Ratio is 3:1 copyright cmassengale 32
    33. 33. What Do the Peas Look Like? copyright cmassengale 33
    34. 34. …And Now the Test CrossMendel then crossed a pure & a hybrid from his F2 generationThis is known as an F2 or test crossThere are two possible testcrosses: Homozygous dominant x Hybrid Homozygous recessive x Hybrid copyright cmassengale 34
    35. 35. F2 Monohybrid Cross (1st)Trait: Seed ShapeAlleles: R – Round r – WrinkledCross: Round seeds x Round seeds RR x Rr Genotype: RR, Rr R r Phenotype: Round Phenotype R RR Rr Genotypic Ratio: 1:1 R RR Rr Phenotypic Ratio: All alike copyright cmassengale 35
    36. 36. F2 Monohybrid Cross (2nd)Trait: Seed ShapeAlleles: R – Round r – WrinkledCross: Wrinkled seeds x Round seeds rr x Rr R r Genotype: Rr, rr Phenotype: Round & Phenotype r Rr rr Wrinkled G. Ratio: 1:1 r Rr rr P.Ratio: 1:1 copyright cmassengale 36
    37. 37. F2 Monohybrid Cross ReviewHomozygous xheterozygous(hybrid)Offspring:50% Homozygous RR or rr50% Heterozygous Rr Phenotypic Ratio is 1:1 Called Test Cross because theoffspring have SAME genotype asparents copyright cmassengale 37
    38. 38. Practice Your CrossesWork the P1, F1, and both F2 Crosses for each of the other Seven Pea Plant Traits copyright cmassengale 38
    39. 39. Mendel’s Laws copyright cmassengale 39
    40. 40. Results of Monohybrid CrossesInheritable factors or genes are responsible for all heritable characteristicsPhenotype is based on GenotypeEach trait is based on two genes, one from the mother and the other from the fatherTrue-breeding individuals are homozygous ( both alleles) are the same copyright cmassengale 40
    41. 41. Law of DominanceIn a cross of parents that arepure for contrasting traits, onlyone form of the trait will appear inthe next generation.All the offspring will beheterozygous and express only thedominant trait.RR x rr yields all Rr (round seeds) copyright cmassengale 41
    42. 42. Law of Dominance copyright cmassengale 42
    43. 43. Law of SegregationDuring the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring. copyright cmassengale 43
    44. 44. Applying the Law of Segregation copyright cmassengale 44
    45. 45. Law of Independent AssortmentAlleles for different traits are distributed to sex cells (& offspring) independently of one another.This law can be illustrated using dihybrid crosses. copyright cmassengale 45
    46. 46. Dihybrid CrossA breeding experiment that tracks the inheritance of two traits.Mendel’s “Law of Independent Assortment”a. Each pair of alleles segregates independently during gamete formationb. Formula: 2n (n = # of heterozygotes) copyright cmassengale 46
    47. 47. Question: How many gametes will be producedfor the following allele arrangements? Remember: 2n (n = # of heterozygotes) 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtQq copyright cmassengale 47
    48. 48. Answer:1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry2. AaBbCCDd: 2n = 23 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64gametes copyright cmassengale 48
    49. 49. Dihybrid CrossTraits: Seed shape & Seed colorAlleles: R round r wrinkled Y yellow y green RrYy x RrYy RY Ry rY ry RY Ry rY ry All possible gamete combinations copyright cmassengale 49
    50. 50. Dihybrid Cross RY Ry rY ryRYRyrYry copyright cmassengale 50
    51. 51. Dihybrid Cross RY Ry rY ryRY RRYY Round/Yellow: 9 RRYy RrYY RrYyRy RRYy Round/green: 3 RRyy RrYy Rryy wrinkled/Yellow: 3rY RrYY RrYy rrYY rrYy wrinkled/green: 1ry RrYy Rryy rrYy rryy 9:3:3:1 phenotypic ratio copyright cmassengale 51
    52. 52. Dihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 copyright cmassengale 52
    53. 53. Test CrossA mating between an individual of unknown genotype and a homozygous recessive individual.Example: bbC__ x bbcc BB = brown eyes Bb = brown eyes bb = blue eyes bC b___ bc CC = curly hair Cc = curly hair cc = straight hair copyright cmassengale 53
    54. 54. Test CrossPossible results: bC b___ C bC b___ cbc bbCc bbCc or bc bbCc bbcc copyright cmassengale 54
    55. 55. Summary of Mendel’s laws PARENT LAW OFFSPRING CROSSDOMINANCE TT x tt 100% Tt tall x short tall Tt x Tt 75% tallSEGREGATION tall x tall 25% short 9/16 round seeds & green pods RrGg x RrGgINDEPENDENT 3/16 round seeds & yellow round & green podsASSORTMENT x 3/16 wrinkled seeds & green pods round & green 1/16 wrinkled seeds & yellow pods copyright cmassengale 55
    56. 56. Incomplete Dominance and Codominance copyright cmassengale 56
    57. 57. Incomplete DominanceF1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties.Example: snapdragons (flower)red (RR) x white (rr) r r RR = red flower R rr = white flower R copyright cmassengale 57
    58. 58. Incomplete Dominance r r produces theR Rr Rr F1 generationR Rr Rr All Rr = pink (heterozygous pink) copyright cmassengale 58
    59. 59. Incomplete Dominance copyright cmassengale 59
    60. 60. CodominanceTwo alleles are expressed (multiple alleles) in heterozygous individuals.Example: blood type 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii copyright cmassengale 60
    61. 61. Codominance ProblemExample: homozygous male Type B (IBIB) x heterozygous female Type A (IAi) IA i I B IAIB IBi 1/2 = IAIB 1/2 = IBi IB IAIB IBi copyright cmassengale 61
    62. 62. Another Codominance Problem• Example: male Type O (ii) x female type AB (IAIB) IA IB i IAi IBi 1/2 = IAi 1/2 = IBi i IAi IBi copyright cmassengale 62
    63. 63. CodominanceQuestion: If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents?boy - type O (ii) X girl - type AB (IAIB) copyright cmassengale 63
    64. 64. CodominanceAnswer: IA iIB IAIB Parents: genotypes = IAi and IBi phenotypes = A and Bi ii copyright cmassengale 64
    65. 65. Sex-linked TraitsTraits (genes) located on the sex chromosomesSex chromosomes are X and YXX genotype for femalesXY genotype for malesMany sex-linked traits carried on X chromosome copyright cmassengale 65
    66. 66. Sex-linked Traits Example: Eye color in fruit flies Sex Chromosomes fruit fly eye colorXX chromosome - female Xy chromosome - male copyright cmassengale 66
    67. 67. Sex-linked Trait ProblemExample: Eye color in fruit flies (red-eyed male) x (white-eyed female) XRY x XrXrRemember: the Y chromosome in males does not carry traits. Xr XrRR = red eyedRr = red eyed XRrr = white eyedXY = maleXX = female Y copyright cmassengale 67
    68. 68. Sex-linked Trait Solution: Xr Xr 50% red eyedXR X X X X R r R r female 50% white eyedY Xr Y Xr Y male copyright cmassengale 68
    69. 69. Female Carriers copyright cmassengale 69
    70. 70. Genetic Practice Problems copyright cmassengale 70
    71. 71. Breed the P1 generationtall (TT) x dwarf (tt) pea plants t t T T copyright cmassengale 71
    72. 72. Solution:tall (TT) vs. dwarf (tt) pea plants t t Tt Tt produces theT F1 generationT Tt Tt All Tt = tall (heterozygous tall) copyright cmassengale 72
    73. 73. Breed the F1 generationtall (Tt) vs. tall (Tt) pea plants T t T t copyright cmassengale 73
    74. 74. Solution: tall (Tt) x tall (Tt) pea plants T t produces the TT Tt F2 generationT 1/4 (25%) = TT Tt tt 1/2 (50%) = Ttt 1/4 (25%) = tt 1:2:1 genotype 3:1 phenotype copyright cmassengale 74
    75. 75. copyright cmassengale 75

    ×