GENETICS PROBLEMS - Incomplete Dominance 
BIOL 1406
 
 

Gene information for first two problems: In a certain stain of chickens, feather color is determined by a pair of alleles that show incomplete dominance.  The two alleles are Fb and Fw.  A chicken that is black has the genotype Fb and Fb.  A chicken that is white has the genotype Fw Fw and a chicken that is heterozygous (Fb Fw) would have blue feathers. 

 
1. If a black feathered chicken is cross with a white feathered chicken, what color would the offspring be?
 
 
2. If two blue feathered chickens were crossed, what is the expected phenotype ratio of their offspring?
 
 
 

Gene information for next problems: Crosses between red (CrCr) and white (CwCw) shorthorn cattle result in roan (CrCw) offspring.  This is an example of incomplete inheritance.  The presence or absence of horns is a separate gene with regular dominant and recessive alleles.  Polled (hornless) cattle show the dominant trait (H) and horned cattle have the recessive trait (h).

 
3. A bull is homozygous polled and is red in color.  He is mated with a horned, roan cow.  What are the expected phenotypes in their offspring and the percentage chance for each?
 
 
4. A roan bull that is heterozygous polled is mated with a white heterozygous polled cow.  What would be the expected phenotypes of their offspring and what is the expected chance of each?
 
 
 

Gene information for next problems: In snapdragons, the alleles for flower color show incomplete dominance. CRCR produces red flowers; CWCW produces white flowers and CRCW produces pink flowers.  The height of the plant is determined by a separate gene with regular dominant and recessive alleles.  Normal height (D) is dominant over dwarf height (d).

 
5. A snapdragon that is heterozygous normal in height and has white flowers is crossed with a plant that is dwarf in height and has red flowers.  What is the expected phenotype ratio in the offspring?
 
 
6. A plant that is homozygous normal in height and has ping flowers is crossed with a dwarf plant that has pink flowers.  What is the expected phenotype ratio in the offspring?