Incomplete Dominance vs. Codominance: Beyond Dominant and Recessive Problems (p 274)

  1. Define Incomplete dominance.

Incomplete dominance in human hypercholesterolemia

  • Receptors on liver cells take LDL cholesterol out of the blood
  1. A couple who are expecting their first baby. The woman’s cholesterol is 2x normal levels because she genotype is Heterozygous (Hh). Her husband has normal cholesterol levels (HH)
  2. Complete a punnett square.
  1. The probability that the baby will have…
  • Normal cholesterol levels is ______%.
  • High cholesterol levels is _____%
  • VERY high cholesterol levels is _____%

4 O’clock flowers & Incomplete dominance

  • The allele for white is W.
  • The allele for Red is R.
  1. What would happen if two Pink (RW) 4 O’clock flowers were crossed?
  2. Complete a Punnett square
  1. What is the genotype ratio ___RR: ___ RW: ___WW
  1. What is the phenotype ratio ___Red: __ Pink: ___white
  1. ______True/False: If you know the phenotype(physical appearance), you do NOT know the genotype(2 letter combination).

Human Hair:

C = Curly alleles S = Straight allele

CC – genotype CS - genotypeSS – genotype

Curly- phenotype Wavy – phenotype Straight - phenotype

  1. A woman with naturally curly hair is pregnant. The baby’s father has wavy hair.
  2. Complete a Punnett Square
  3. What is the genotype ratio ___CC: ___ CS: ___SS
  1. What is the phenotype ratio ___Curly: __ Wavy: ___straight
  1. Define Codominance.

Chicken feathers exhibit Codominance.

  • The allele B codes for Black feathers
  • The allele W codes for White feathers.
  1. What would happen if a Black chicken (BB) were crossed with a “Erminette” – black and white speckled roster (BW)
  2. Complete the Punnette square 
  3. What is the expected genotype ratio

___BB: __BW: ___WW

  1. What is the expected phenotype ratio

___ Black: __: “Erminette”: ___ white.

Horse Hair exhibits Codominance

  • The allele R codes for Red hair
  • The allele W codes for White hair
  • A Roan colored horse has the genotype RW and will produce both Red & White hairs
  1. A Roan colored female (RW) is breed with a Roan colored male (RW)
  2. Complete the punnett Sq
  3. The possibility that the offspring will have…
  • A Red haired coat is ______%
  • A Roan haired coat is ______%
  • A white haired coat is ______%

Blood type Exhibits Codominance

  • Blood typeAB is the equal expression of the two alleles IAand IB
  • We will ignore blood type O until another lesson
  1. What possible blood types could a baby have, if both parents have blood type AB (genotype IAand IB )
  1. The baby’s would have a ______% of having blood type A
  1. The baby would have a ______% chance of having blood type B
  1. The baby would have a ______% chance of having blood type AB