Multiple Choice
Which of the following describes the 3D structure of multiple polypeptide chains in a single protein?
396
views
2
rank
11. Translation
Proteins
2:44 minutesProblem B.5
Textbook Question
Describe the gene and protein defects in phenylketonuria (PKU). How are these defects connected to disease symptoms?
Verified step by step guidance1
Step 1: Understand that phenylketonuria (PKU) is caused by mutations in the gene encoding the enzyme phenylalanine hydroxylase (PAH), which is responsible for converting the amino acid phenylalanine into tyrosine.
Step 2: Recognize that the gene defect leads to a deficient or nonfunctional PAH enzyme, resulting in an inability to metabolize phenylalanine properly.
Step 3: Explain that the protein defect (nonfunctional or deficient PAH enzyme) causes phenylalanine to accumulate in the blood and tissues, leading to toxic levels.
Step 4: Connect the accumulation of phenylalanine to the disease symptoms, such as intellectual disability, developmental delays, and neurological problems, due to its toxic effects on brain development and function.
Step 5: Summarize that the gene mutation causes a defective enzyme, which disrupts normal metabolism of phenylalanine, and this metabolic block leads directly to the clinical manifestations of PKU.
Verified video answer for a similar problem:This video solution was recommended by our tutors as helpful for the problem above
Video duration:
2mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Phenylketonuria (PKU) and its Genetic Basis
PKU is an inherited metabolic disorder caused by mutations in the PAH gene, which encodes the enzyme phenylalanine hydroxylase. This enzyme is responsible for converting phenylalanine to tyrosine. Defects in the PAH gene lead to reduced or absent enzyme activity, causing phenylalanine accumulation.
Recommended video:
Guided course
07:43
Genetic Cloning
Role of Phenylalanine Hydroxylase Enzyme
Phenylalanine hydroxylase catalyzes the hydroxylation of phenylalanine to tyrosine, a precursor for neurotransmitters. When this enzyme is defective, phenylalanine builds up to toxic levels, disrupting normal brain development and function, which underlies the neurological symptoms of PKU.
Recommended video:
Connection Between Molecular Defects and Disease Symptoms
The accumulation of phenylalanine and its metabolites in PKU leads to neurotoxicity, causing intellectual disability, seizures, and behavioral problems. The lack of tyrosine also impairs neurotransmitter synthesis, further contributing to cognitive and developmental issues seen in untreated PKU patients.
Recommended video:
Guided course
09:12Transgenic Organisms and Gene Therapy
Related Videos
Related Practice