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Notes: Types of Inheritance

Notes: Types of Inheritance. Test Cross. Used to determine the genotype of an individual that displays a dominant trait. Either PP or Pp. Test Cross. Used to determine the genotype of an individual that displays a dominant trait. Either PP or Pp

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Notes: Types of Inheritance

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  1. Notes: Types of Inheritance

  2. Test Cross • Used to determine the genotype of an individual that displays a dominant trait. • Either PP or Pp

  3. Test Cross • Used to determine the genotype of an individual that displays a dominant trait. • Either PP or Pp • Cross with homozygous recessive (pp) • If in the offspring, there are pp, then the parent had to be Pp

  4. Types of Inheritance • Complete Dominance • Incomplete Dominance • Codominance • Sex-linked • Polygenic • Epistasis You will be responsible to complete punnett squares for the types bolded

  5. Complete Dominance • One allele is completely dominant over the other • Only two phenotypes exist • One phenotype is masked • The heterozygous phenotype shows dominant trait • Ex: Purple flowers are dominant to white • PP= purple • Pp= purple • pp= white

  6. Complete Dominance Autosomal Genetic Disorders. Carrier: A heterozygote for a recessive disorder (ex/ Cc). • Carrier does not show symptoms but can pass recessive allele to offspring • Affected person must inherit two recessive alleles • Example Cystic Fibrosis, Tay-sachs, sickle-cell anemia • CC &Cc = unaffected • cc = affected

  7. Practice Problem A male and female are both carriers for sickle-cell anemia. What percent chance do they have of having a child with sickle-cell anemia?

  8. Incomplete Dominance • Neither allele is completely dominant over the other

  9. Incomplete Dominance • Neither allele is completely dominant over the other • Three phenotypes exist • The heterozygous phenotype shows blended trait

  10. Incomplete Dominance • Neither allele is completely dominant over the other • Three phenotypes exist • The heterozygous phenotype shows blended trait • Ex: Flowers can be pink, red, or white. • RR=red • WW= white • RW =pink RR RW WW

  11. Incomplete Dominance • Cross two pink flowers • What percent of their offspring will have white flowers?

  12. Fish can be green (GG), blue (BB), or teal (GB) Green (GG) Teal (GB) Blue (BB)

  13. Codominance • Both alleles are dominant

  14. Codominance • Both alleles are dominant • Three phenotypes exist • Neither phenotype is masked • The heterozygous phenotype shows both traits at once

  15. Codominance • Both alleles are dominant • Three phenotypes exist • Neither phenotype is masked • The heterozygous phenotype shows both traits at once. X = red (RR) white (WW)

  16. Codominance • Both alleles are dominant • Three phenotypes exist • Neither phenotype is masked • The heterozygous phenotype shows both traits at once. X = red (RR) white (WW) red & white(WR)

  17. Codominance EX: In Smileys, eye shape can be starred, circular, or a circle with a star. Write ALL the phenotypes and genotypes that exist.

  18. Codominance EX: In Smileys, eye shape can be starred, circular, or a circle with a star. Write ALL the phenotypes and genotypes that exist. CC = circle SS = star SC = circle-star

  19. Codominance • Example: Blood Types • Trait controlled by three alleles, with two that are codominant and one recessive IA : produces A antigens on surface of cell IB : produces B antigens i: does not produce antigens

  20. Practice Problem • What possible blood types could the children of a homozygous A female and a male with AB blood have? • Parents Genotype _______X ________

  21. Sex Linked • Disorder/trait found on the “X” chromosome • Which gender has more instances of having an x-linked disorder? • Men-Males have no second copies of X-linked genes (XY). • Females have two X chromosomes (XX) so if one has a defect they can use the other normal X chromosome.

  22. Sex-Linked • EX: color blindness • Punnett square determines sex and trait • First, Use X and Y to show gender • Second, use a letter on the X chromosome to show which allele they inherited.

  23. Sex-Linked • EX: color blindness • Punnett square determines sex and trait • First, Use X and Y to show gender • Second, as a letter on the X chromosome to show which allele they inherited. Possible genotypes and phenotypes: XR XR = Female, normal vision XR Xr= Female, normal vision XrXr= Female, color blind XR Y = Male, normal vision XrY = Male, color blind

  24. Sex Linked What percentage of offspring would be color blind if a female carrier and a male who has normal vision had children?

  25. Sex Linked What percentage of offspring would be color blind if a female carrier and a male who has normal vision had children? Step 1: Determine genotype of parents ____________ x ____________

  26. Sex Linked Step 2: set up and complete punnett square. What percent of their children would be colorblind?

  27. Polygenic Many genes may interact to produce one trait Ex: Skin color result of four genes that interact to produce range of colors

  28. Epistasis One gene controls many traits EX: Albinism Albinos are unable to synthesize melanin, the pigment molecule responsible for most human coloring

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