Tail length in a certain species of armadillo falls along a continuum; a plot of tail length versus frequency displays a normal distribution. Assuming that environmental factors do not play an important role in determining tail length, this type of variation probably reflects __________.

• A. pleiotropy
• B. epistasis
• C. complete dominance
• D. incomplete dominance
• E. polygenic inheritance

Answer: (E)

Verified step by step guidance

1. Understand the concept of polygenic inheritance: Polygenic inheritance involves multiple genes contributing to a single trait, resulting in a continuous range of phenotypes, such as tail length in armadillos.
2. Recognize the characteristics of a normal distribution: A normal distribution is a bell-shaped curve that indicates a continuous variation in a trait, which is typical for polygenic traits.
3. Consider the role of environmental factors: The problem states that environmental factors do not play an important role, suggesting that genetic factors are primarily responsible for the variation in tail length.
4. Differentiate between the given options: Pleiotropy involves one gene affecting multiple traits, epistasis involves interaction between genes, complete dominance results in one allele completely masking another, and incomplete dominance results in a blend of traits. None of these options explain a continuous variation like polygenic inheritance does.
5. Conclude that polygenic inheritance is the most likely explanation for the continuous variation in tail length, as it involves multiple genes contributing to the trait, resulting in a normal distribution.