Some traits are considered to be quantitative, even though phenotypes are classified only as present or absent. Genetic diseases often fit this description.

1. What is the term used to describe this type of trait?

a. Polygenic trait

b. Threshold trait

c. Meristic trait

d. Epistatic trait O environmental trait

2. What creates the underlying quantitative distribution for this type of trait?

a.Many genes can code for the trait, but only one gene promotes or inhibits expression of the others, resulting in the presence or absence of the trait

b. There are many alleles for the trait at a single locus. Some of the alleles cause the present phenotype and some cause the absent phenotype.

c. The trait is present or absent, but the severity varies and because measurements are subjective. the trait is classified only as present or absent.

d. Genetic and environmental factors determine an individual's susceptibility to the trait. Susceptibility exhibits continuous variation, and individuals above a certain threshold express the trait.