A hypothetical condition in some domesticated fowl is identified phenotypically by patchy loss of feathers on the animals' backs. Although several factors, genetic and environmental, are found to be involved, only about 3% of any population with any of these factors are found with feather loss. Which of the following is a likely cause?
A)continuous variation
B)threshold of liability
C)low mutation frequency
D)high number of alleles in one of the genes
E)high number of environmental effects

Question

Quizplus · Accepted Answer

The presence of multiple factors and low frequency of the condition suggests that it may be controlled by a threshold of liability, meaning that a certain combination or threshold of factors must be present for the phenotype to be expressed.

A Hypothetical Condition in Some Domesticated Fowl Is Identified Phenotypically