Non Mendelian Genetics

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Non Mendelian Genetics
Patterns of inheritance that arent simply
dominant or recessive
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I. Incomplete Dominance

• The phenotype of a heterozygous individual is
  intermediate between those of the two
  homozygotes.
• B. Examples
• 1. Snap Dragons When red and white flowers are
  crossed all the F1 offspring will have pink
  flowers
• 2. Horses When a chestnut colored horse is
  bred with a cremello (white) colored horse the
  offspring are palomino color.

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II. Co-dominance

• The phenotypes of both homozygotes are produced
  in the heterozygous individuals both alleles are
  expressed equally.
• B. Examples
• 1. Short-horned cattle red and white coats are
  co-dominant
• 2. Chickens feather color black and white are
  co-dominant
• 3. Four oclock plants red and white petals are
  co-dominant

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Four oclock plants
Short-horned cattle
Black and white feathers
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III. Multiple Alleles

• Traits controlled by more than 2 alleles.
• B. Examples
• 1. ABO blood type in humans A and B are
  codominant, but dominant to O
• 2. Pigeons feather color BA, B and b BA
  produces ash red feathers, B produces wild-type
  (grey) feathers, and b produces chocolate colored
  feathers

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IV. Polygenic Inheritance

• Many traits are controlled by 2 or more genes.
• B. Examples
• 1. Eye color
• 2. Hair color
• 3. Skin color
• 4. Height

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Eye Color
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Skin Color
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V. Traits Influenced by the Environment

• An individuals phenotype often depends on
  conditions in the environment.
• B. Such factors as temperature, amount of
  sunlight, soil conditions and nutrition can
  affect the phenotype of an organism.
• C. Examples
• 1. Arctic fox brown in summer white in winter
• 2. Hydrangea flower color acidity of the soil
  determines blue or reddish color
• 3. Siamese cats cooler body areas are darker
• 4. Height in humans - early nutrition (or lack
  of) affects the height of humans

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The End!
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