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:

To determine the best description of glaucoma, we analyze each option:

• Recessive trait (first option): Requires two recessive alleles, but glaucoma is linked to three genes and 20+ loci, not just recessive alleles. Eliminate.
• Polygenic trait (second option): Polygenic traits are influenced by multiple genes (alleles of several genes). Glaucoma is linked to three genes and over 20 genetic loci, fitting polygenic.
• Codominant trait (third option): Codominance involves both alleles expressed equally, not related to multiple loci here. Eliminate.
• Dominant trait (fourth option): Dominant traits need one dominant allele, but glaucoma involves multiple genes, not just one dominant allele. Eliminate.

Answer:

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