Module 10 patterns of inheritance
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Module 10 patterns of inheritance

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Module 10 patterns of inheritance Presentation Transcript

  • 1. Genetics the study of heredity
  • 2. 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
  • 3. 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
  • 4. 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
  • 5. 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)
  • 6.
    • Genotype: letters used for the alleles
      • ex: PP, Pp, pp
    • Phenotype: what an organisms looks like
      • ex: purple, white
  • 7. 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
  • 8. 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
  • 9. 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
  • 10.
    • 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
  • 11. 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
  • 12. 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
  • 13. 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
  • 14. 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
  • 15. 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
  • 16.
    • 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
  • 17.
      • 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
  • 18.
    • 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
  • 19.
    • 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
  • 20. 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
  • 21.
    • 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
  • 22.
    • 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
  • 23.
    • 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.
  • 24.
    • If 2 individuals with Type AB blood marry, what percentage of their offspring will have Type AB blood?
    Practice A B A B
  • 25.
    • 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?
  • 26. 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