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 the options:

• A recessive trait requiring multiple recessive alleles (first option) is incorrect because glaucoma is linked to three genes and over 20 genetic loci, not just multiple recessive alleles.
• A polygenic trait is influenced by multiple genes. Since glaucoma is linked to three genes and more than 20 genetic loci, it is polygenic. This matches the second option.
• A codominant trait (third option) is expressed when both alleles are dominant and expressed equally, which does not fit glaucoma's genetic linkage.
• A dominant trait depending on one dominant allele (fourth option) is incorrect as glaucoma involves multiple genes/loci, not a single dominant allele.

Answer:

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