Question

glaucoma is a leading cause of blindness. studies have linked a common form of glaucoma to three genes and more than 20 genetic loci. which best describes glaucoma?
a recessive trait that requires multiple recessive alleles to be expressed
a polygenic trait that is influenced by the alleles of several genes
a codominant trait that is expressed more often when more dominant alleles are present
a dominant trait that depends on the presence of only one of many dominant alleles

Explanation:

Polygenic traits are influenced by multiple genes. Since glaucoma is linked to three genes and more than 20 genetic loci, it fits the definition of a polygenic trait.

Answer:

a polygenic trait that is influenced by the alleles of several genes