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Beyond Mendel

Beyond Mendel. Incomplete Dominance Codominance Multiple Alleles. Beyond Dominant and Recessive Alleles. Incomplete Dominance : when neither allele is completely dominant over the other.  Results in the heterozygous phenotype being a blending of the two homozygous phenotypes.

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Beyond Mendel

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  1. Beyond Mendel Incomplete Dominance Codominance Multiple Alleles

  2. Beyond Dominant and Recessive Alleles • Incomplete Dominance:when neither allele is completely dominant over the other.  • Results in the heterozygous phenotype being a blending of the two homozygous phenotypes.

  3. A capital letter represents one of the incompletely dominant alleles. • The same capital letter prime (P’) represents the other incompletely dominant allele so that the two do not get mixed up. • There is a second way to represent using two different capital letter

  4. In snapdragons, red flower color (RR) is incompletely dominant to white (R’R’) flower color. A heterozygous snapdragon is pink (RR’). Cross a pink snapdragon with a pink snapdragon. RR’ X RR’ Genotypic Ratio: Phenotypic Ratio:

  5. Codominance: when both alleles are dominant. • The heterozygous individual shows both alleles expressed equally. • A capital letter represents one of the codominant alleles. • A different capital letter represents the other codominant allele so that the two do not get mixed up.

  6. In chickens, black feather color (BB) is codominant to white feather color (WW).  Both feather colors show up in a checkered pattern in the heterozygous individual (BW). Cross a checkered chicken with a checkered chicken. • __________      X      ________ Genotypic Ratios: Phenotypic Ratios:

  7. Multiple Alleles:when more than two different alleles exist for the same trait. • (Remember: each individual will only have two alleles for a trait but there are several alleles to choose from.)

  8. In humans, blood type has multiple alleles.  IA and IB are codominant and i (type O blood) is recessive.

  9. Some traits (blood types) show both codominance and multiple alleles

  10.  Cross a heterozygous type A with a heterozygous type B. _____________  X  __________ Genotypes: Phenotypes:

  11. Cross a person with type AB blood with another person with type O blood. ____________  X  __________ Genotypes: Phenotypes:

  12. Polygenic Inheritance:the inheritance pattern is controlled by two or more genes each with two alleles. • Polygenic inheritance usually shows up as a range of variation such has height, skin color or hair color.

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