Which statement best describes alleles in terms of phenotype?

Prepare for the Clinical Genetics Test. Utilize flashcards and multiple-choice questions, each with hints and explanations. Achieve success on your exam!

Alleles are different versions of the same gene, and the phenotype—the observable traits—reflect which versions you inherit along with how those versions interact with each other and with the environment. An allele can change how much of a gene product is made or how well it works, leading to variations in traits. Many alleles have no disease effect or only subtle effects, while others can contribute to disease under certain circumstances. Importantly, alleles can reside in coding regions or in regulatory/noncoding regions, and both can influence phenotype. So, alleles may produce differences in phenotype because they can alter protein function or gene expression, not because they always cause disease or never affect traits.