Use the paragraph to answer the question. The condition phenylketonuria, or PKU, is caused by the toxic buildup of the amino acid phenylalanine, which is found in all proteins and even some artificial sweeteners. The build up in the blood affects nerve and brain development. PKU is caused by a mutation in a gene that affects the breakdown of phenylalanine. When foods that contain phenylalanine are removed from the diet, the effects of PKU are reduced.

Which statement is true about expressed traits of PKU and environmental factors?

(1 point)

Nerve and mental problems are an expressed trait of the PKU mutation regardless of environmental factors.

Blood circulation problems are an expressed trait of the PKU mutation regardless of environmental factors.

Blood circulation problems are a trait in PKU patients caused by the environmental factor of eating phenylalanine foods.

Nerve and mental problems are a trait in PKU patients caused by the environmental factor of eating phenylalanine foods.