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) high number of alleles in one of the genes
C) low mutation frequency
D) threshold of liability
E) high number of environmental effects

Question

Quizplus · Accepted Answer

The condition described is likely caused by a threshold of liability, which means that the feather loss occurs only when a certain threshold of genetic and environmental factors is surpassed. This explains why only a small percentage of the population shows the phenotype despite the presence of multiple contributing factors.

A Hypothetical Condition in Some Domesticated Fowl Is Identified Phenotypically