Question

glaucoma is a leading cause of blindness. studies have linked a common form of glaucoma to three genes with 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:

A polygenic trait is influenced by multiple genes. Since glaucoma is linked to more than 20 genetic loci, it fits the definition of a polygenic trait. A recessive trait (first option) would be related to a single - gene recessive inheritance pattern, which is not indicated here. Codominance (third option) is about both alleles being expressed in a heterozygote, not relevant to multiple genes. A dominant trait (fourth option) depending on one dominant allele is also incorrect as multiple genes are involved.

Answer:

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