Question

Choose a single-gene disease and describe how environmental factors may affect the phenotype.

Short answer

Phenylketonuria or PKU is a single-gene disease caused by mutations in the PAH gene. This disruption leads to an inability to break down the amino acid phenylalanine, resulting in some severe symptoms when phenylalanine levels get high. A diet high in protein (and thereby phenylalanine) can exacerbate this condition, while diets low in phenylalanine can help manage it. Hence, the environment, here being dietary intake, can affect the phenotype of PKU.

Step-by-step solution

Choosing a Single-Gene Disease

Choose a disease caused by mutations in a single gene. For instance, you can choose Phenylketonuria (PKU). PKU is a genetic disorder resulting from mutations in the PAH gene, which makes Phenylalanine Hydroxylase, an enzyme breaking down the amino acid phenylalanine.

Understanding the Disease and Its Genetic Basis

Understand the biology of the chosen disease- in this case, PKU. People with PKU lack functional Phenylalanine Hydroxylase, leading to a buildup of phenylalanine. When Phenylalanine levels get very high, individuals may suffer from symptoms like intellectual disability, seizures, and other neurologic problems.

Identifying Environmental Influences

Determine potential ways the environment plays a role in exacerbating or alleviating the symptoms. For PKU, it's known that diet plays a huge role. Since phenylalanine is found in most proteins, a diet low in phenylalanine can help manage the disease, while a high-protein diet can worsen it.