Inheritance Patterns:

Simple Mendelian

Incomplete Dominance

Codominance

Multiple Alleles

Sex-Linked

Polygenic

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Other Patterns of Inheritance:�Breaking the Rules!

• 2 Possible Phenotypes:
• Dominant or Recessive�
• Examples:
• Tall or short plants
• Green or yellow pods
• Pink or orange skin

Review:�Simple Genetics (Mendelian)

• Incomplete Dominance = when the phenotype for the heterozygous individual is intermediate to the dominant phenotype and the recessive phenotype.
• 3 Possible Phenotypes
• Dominant, Recessive, or Heterozygous (blend of the other two = in between)

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Incomplete Dominance

• EXAMPLES:
• Red and White Snapdragons produce Pink Snapdragons.

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• Black and White Chickens produce Gray/blue chickens.

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• Big and Small produce a Medium size.

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Incomplete Dominance

Incomplete Dominance Example

• Pink snapdragons are crossed with Red snapdragons. What is the probability of Red? White? Pink?
• Parents: Pink x Red
• Genotypes: RW x RR
• OFFSPRING:
• RED =
• WHITE =
• PINK =

• Identify THREE phenotypes
• Red, White, or Pink
• Identify the genotypes. *You have the option to use two different letters*
• RED = RR
• WHITE = WW
• PINK= RW

50%

0%

50%

Incomplete Dominance Example

R W

R

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R

RR RW

RR RW

(RR or rr)

(RR or rr)

(Rr)

Incomplete Dominance Example

Incomplete Dominance Example

Codominant Inheritance

• Co = TOGETHER
• Codominance is the expression of BOTH alleles at the same time.
• Allows the phenotypes of both alleles to be equally expressed in the heterozygous individual.
• 3 Possible Phenotypes:
• Dominant 1, Dominant 2, or Heterozygous (both phenotypes are expressed TOGETHER).

Codominant Inheritance

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• Examples:
• Pink flower and white flower make pink & white speckled flowers.
• Red cow and white cow make roan cows (both white and red patches).
• Black feathered chickens and white feathered chickens make speckled chickens.
• Type A blood and Type B blood make Type AB blood.

• Identify THREE phenotypes for coat color.
• Red, White, or Roan

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• Identify the genotypes.
• Choose C as base for Coat Color.
• Use TWO DIFFERENT LETTERS as superscripts for Red and White alleles.
• Both are capitalized since both are dominant.

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• RED = C^RC^R
• WHITE = C^WC^W
• ROAN = C^RC^W

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In cattle, Coat color may be White, Red, or a mix of both Red and White called ROAN. A Red bull and a White cow are bred.

• What are the genotypes of the parents?

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• What is the probability of red cattle?

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• White?

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• Roan?

Codominant Inheritance Example

C^R C^R

C^W

C^W

0 %

0 %

100 %

C^RC^W C^RC^W

C^RC^W C^RC^W

C^RC^R x C^WC^W