All AP Biology Resources
Example Questions
Example Question #1 : Understand Incomplete Dominance
A white homozygous recessive plant is crossed with a homozygous dominant red plant. The plants produced from this cross are all pink. What kind of inheritance does this plant's color follow?
Multiple alleles
Sex-linked dominance
Codominance
Incomplete dominance
Complete dominance
Incomplete dominance
In incomplete dominance, heterozygotes express an intermediate phenotype. Since neither parent expresses the pink phenotype, we know that plant color follows incomplete dominance since neither red nor white is fully expressed as would be the case with complete dominance; rather they are both incompletely expressed.
Example Question #2 : Understand Incomplete Dominance
Which occurs when a heterozygous genotype produces blended traits?
Incomplete dominance
Codominance
Monosomy
Trisomy
Pure genotype
Incomplete dominance
Incomplete dominance involves expression of an intermediate phenotype. The heterozygotes express a phenotype that is a blend of both the dominant and recessive phenotypes. One common example is a flower with white petals and a flower with red petals sexually reproduce to create flowers with pink petals.
Example Question #3 : Understand Incomplete Dominance
Which of these is an example of polygenic inheritance?
Sickle cell anemia
Freckles
Color blindness
Skin color
Duchenne muscular dystrophy
Skin color
Polygenetic inheritance is where multiple genes affect a single trait. Human skin color depends on three sets of alleles: Aa, Bb, and Cc. A cross between two parents with any combination of these three alleles determines skin color; there is no single skin color gene.
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