Module 10 patterns of inheritance
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Module 10 patterns of inheritance

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    Module 10 patterns of inheritance Module 10 patterns of inheritance Presentation Transcript

    • Genetics the study of heredity
    • Gregor Mendel “Father of Genetics”
      • Heredity -the transfer of characteristics from parents to offspring through their genes
      • Gregor Mendel -used garden peas to study heredity
    • Mendel’s Experiments
      • cross fertilization : Mendel crossed two parent plants with opposite traits (purple x white). This was the Parental generation (P). The First generation (F1) were identical (purple).
      • self fertilization : Mendel allowed the purple flowers from the First generation (F1) to self-pollinate. Self pollination produced the Second generation (F2).
      Muskopf, Shannan
    • Mendel’s Conclusions
      • The F1 generation all showed the purple trait (called the dominant trait)
      • In the F2 generation the (white) trait reappears in ¼ of the flowers (called the recessive trait)
      • Each flower has two alleles that determine the appearance
      • The alleles are represented by letters (uppercase letter represents the dominant allele; lowercase letter represents the recessive allele)
      • P is dominant and represents purple
      • p is recessive and represents white
      • The Dominant Is Expressed No Matter What
      • Need 2 Copies Of The Recessive Allele In Order To Be Expressed
      • PP = purple flower Pp = purple flower pp = white flower
    • Alleles
        • homozygous: organisms that have 2 identical alleles for a trait (could be two capital or two lowercase letters)
          • PP
          • pp
        • heterozygous: organisms that have 2 different alleles for a trait
          • ex: Pp (the dominant allele P is expressed so this flower would be purple)
      • Genotype: letters used for the alleles
        • ex: PP, Pp, pp
      • Phenotype: what an organisms looks like
        • ex: purple, white
    • Punnett square
      • A Punnett square is used to show the possible allele combinations in the offspring of 2 parents.
      • Monohybrid cross = cross involving only 1 trait
      The four boxes represent the four possible offspring
    • A plant heterozygous with green peas (Gg) is crossed with a plant that has yellow peas (g).
      • Step 1: Choose a letter for the alleles (green is dominant; yellow is recessive)
          • G : green pea g: yellow pea
      • Step 2: Write the genotypes of the parents
          • heterozygous plant with green peas : Gg
          • plant with yellow peas: gg
          • parents: Gg x gg
      Example of a Monohybrid Cross
    • Step 3: Set up the punnett square with one parent on each side Step 4: Fill out the punnett square middle G g g g gg gg gg gg Gg G g G g G g g g g g g g Gg Gg gg gg Gg G g g g
      • Step 5: Look at the four boxes from Step 5 and determine the genotypes of the four offspring
        • Genotypic ratio: 2 Gg: 2 gg
      • Step 6: Look at the genotypes in Step 6 and determine the phenotypes;
        • Green (G) is dominant over yellow (g), plants that have G in their offspring have green peas
        • Phenotypic ratio: 2 green: 2 yellow
    • Practice-Monohybrid Crosses Cross an individual with blue eyes with an individual with homozygous brown eyes. Brown eyes (B) is dominant to blue eyes (b). Phenotypes: Genotypes: B B b b
    • Cross an individual with blue eyes with an individual with homozygous brown eyes. Brown eyes (B) is dominant to blue eyes (b). Phenotypes: All Brown Eyes Genotypes: All Bb B B b Bb Bb b Bb Bb
    • Practice-Monohybrid Crosses A child is diagnosed with a recessive genetic disease. Neither parent has the disease. What are the genotypes of the parents? Phenotypes: Genotypes: N ? ? nn N
    • A child is diagnosed with a recessive genetic disease. Neither parent has the disease. What are the genotypes of the parents? Genotypes of the parents are Nn N n n Nn nn N NN nn
    • Incomplete Dominance = Blending
      • In snapdragons, there is not a dominant allele. The flower color can be red, pink, or white. A heterozygous flower (Rr) will a blending of red and white (pink).
      • Muskopf, Shannan. Online Images. The Biology Corner . 20 April 2007. http://www.biologycorner.com/bio1/celldivision-chromosomes.html
      • Co dominance: the recessive & dominant traits appear together (both are dominant, no recessive allele)
        • Ex: Cross a red cow with a white cow . What will the offspring be?
      R R W W
        • phenotype: all red and white speckled
        • genotype: all RW
      W RW RW W RW RW R R Muskopf, Shannan. Online Images. The Biology Corner . 20 April 2007. http://www.biologycorner.com/bio1/celldivision-chromosomes.html
      • Polygenic Traits: “many genes” act together resulting in a range of phenotypes
        • Ex: skin, hair, eye color
      Skin color is a polygenic trait because it shows a range of colors. There is not a dominant and recessive color. Farabee, M.J. “Skin Pigmentation.” 2001. Online Image. Online Biology Book. 5 May 2007. http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookgeninterac t.html
      • Multiple Alleles : genes that have more than two alleles
        • There are four blood types (phenotypes): A, B, AB, and O
        • Blood type is controlled by three alleles: A, B, and O
        • Each individual only inherits two alleles (one from each parent).
        • A and B are codominant
        • O is recessive, two O alleles result in type O Blood
        • Blood Types Possible Genotypes
      • Dominant A AA or AO
      • Dominant B BB or BO
      • Codominant AB AB
      • Recessive O OO
    • Practice: Cross a Type AB with a Type O. AB x OO A B O AO BO O AO BO 1. Set up punnett square with one parent on each side 2. Fill out the punnett square middle What are the possible blood types of the four offspring? Genotype Blood Type 2 AO 2 Type A 2 BO 2 Type B
      • A woman heterozygous for Type A blood marries and a man with Type AB blood. Show the cross and the possible offspring.
      • 1. Write the genotypes of the parents:
          • woman heterozygous for Type A: AO
          • man with Type AB: AB
      • 2. Set up punnett square with one parent on each side and fill in the middle.
      Practice A O A AA AO B AB BO Blood types of possible offspring: AA: Type A blood AO: Type A blood AB: Type AB blood BO: Type B blood
      • If a Type O individual marries a Type B individual can they have
      • offspring with Type O blood? What type of blood can the offspring have?
      Practice B ? O O Blood types of possible offspring: AA: Type A blood AO: Type A blood AB: Type AB blood BO: Type B blood
      • If a Type O individual marries a Type B individual can they have
      • offspring with Type O blood? What type of blood can the offspring have?
      B O O BO OO O BO OO Yes, they can have a child with type O or type B blood.
      • If 2 individuals with Type AB blood marry, what percentage of their offspring will have Type AB blood?
      Practice A B A B
      • 50% of their offspring could be Type AB
      A B A AA AB B AB BB If 2 individuals with Type AB blood marry, what percentage of their offspring will have Type AB blood?
    • Review of Terms
      • Allele A form of a gene
      • Homozygous Both Alleles are the Same
      • Heterozygous Alleles are Different
      • Homozygous Dominant AA
      • Homozygous Recessive aa
      • Heterozygous Aa
      • Genotypic Ratio 2 PP : 2 pp
      • Phenotypic Ratio 2 Purple : 2 White