Name:______Hour:______

Incomplete Dominance and Codominance

Incomplete Dominance

  1. Describe the difference between incomplete dominance and codominance.
  1. In horses, some of the genes for hair color are incompletely dominant. Genotypes are as follows: brown horses are BB, white horses are WW and a BW genotype creates a yellow-tannish colored horse with a white mane and tail, which is called “palomino”. Show the genetic crosses between the following horses and record the genotypic and phenotypic ratiosin percentages or fractions, be specific:

a. brown x white b. brown x palomino c. palomino x palomino

Genotypic ratio: Genotypic ratio: Genotypic ratio:

Phenotypic ratio: Phenotypic ratio: Phenotypic ratio:

  1. Which two colors of horse would you want to breed if you wanted to produce the maximum numbers of palominos in the shortest amount of time?
  1. Aliens on Mars either have one eye (OO) or three eyes (TT) but some end up with two eyes (OT) as a result of incomplete dominance. Use this information to help you complete each section below.
  1. What would happen if you crossed a one-eyed alien with a two-eyed alien? Complete the Punnett square to help you determine the probability for the eyes on each alien.
  1. Give the possible genotypes and phenotypes for the offspring.
  1. What percentage of the offspring would be one-eyed? ______%
  1. What percentage of the offspring would be three-eyed?______%
  1. What percentage would be two-eyed? ______%
  1. What would happen if you crossed two, two-eyed aliens? Complete the Punnett square to help you determine the probability for the eyes on each alien.
  1. Give the possible genotypes and phenotypes for the offspring.
  1. What percentage of the offspring would be one-eyed? ______%
  1. What percentage of the offspring would be three-eyed? ______%
  1. What percentage would be two-eyed? ______%
  1. What would happen if you crossed a one-eyed alien with a three-eyed alien? Complete the Punnett square to help you determine the probability for the eyes on each alien.
  1. If 100 aliens were produced from this cross, how many would you expect to have two eyes?

Codominance

  1. In heffalumps, the genes for stripes are codominant. Genotypes are as follows: horizontal stripes are HH, vertical stripes are VV and a HV genotype creates aheffalump with horizontal AND vertical stripes, referred to as being “plaid”. Show the genetic crosses between the following heffalumps and record the genotypic and phenotypic ratiosin percentages or fractions, be specific:

a. horizontal x vertical b. plaid x plaid c. plaid x horizontal

Genotypic ratio: Genotypic ratio: Genotypic ratio:

Phenotypic ratio: Phenotypic ratio: Phenotypic ratio:

  1. Woozles with the genotype DD will have polka dots on their fur and woozles with the genotype SS will have squares. A woozle with the genotype DS will have BOTH polka dots and squares.
  1. What would happen if you crossed a woozle with polka dots and squares with a woozle that has only polka dots? Complete the Punnett square to help you determine the probability of the woozles’ offspring.
  1. What percentage of the offspring would have only polka dots? ______%
  1. What percentage of the offspring would have only squares?______%
  1. What percentage would have both polka dots and squares? ______%