DNA – March 15, What is one example of a genetic disease? Describe it. 2.Show the cross between a Mom who is heterozygous for polydactyl and a Dad who is homozygous recessive for polydactyl. 3.Using your cross from question 2, what is the probability that the offspring will have more than 5 fingers? What is the probability the offspring will be heterozygous?
Today’s Objective SWBAT – Understand the difference between codominance and incomplete dominance
Incomplete Dominance Neither of the alleles is dominant to the other. – The phenotype of the offspring is a mixture of the two phenotypes of the parents. This results in a BRAND new phenotype – Example: Yellow Cow + Blue Cow = Green Cow
Example: Skin Color
Codominance The phenotype of the offspring is a combination of the phenotypes of both parents. Both alleles are expressed separately and contribute to the offspring’s appearance (Unrealistic) Example: – Striped elephant + a polka dot elephant = striped & polka-dot elephant
Example - Chickens A black-feathered (BB) chicken crossed with a white-feathered (WW) chicken results in a black and white feathered chicken (BW).
Show the Cross - Codominance If a black chicken (BB) and a white chicken (WW) mate, what is that probability that the baby chicken will be black? White? Mixture? What happens if a black and white chicken (BW) mates with another black and white chicken? What is the phenotypic ratio?
Incomplete Dominance?
Codominance?
Incomplete Dominance?
Codominance?
Incomplete Dominance?
Practice Problems Incomplete dominance: B = Black, W = White 1.A black female dog and a white male dog have a litter of puppies. If they have 4 puppies, what does probability predict about the phenotypes of these puppies?
Practice Problems Codominance: R = Red, Y = Yellow 2.A female orange panda mates with a male yellow panda. Show the cross and give the phenotypic and genotypic ratios.