Textbook Question
Answer the following questions for autosomal conditions such as PKU.
If both parents are heterozygous carriers of a mutant allele, what is the chance that their first child will be homozygous recessive for the mutation?
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Ch. 9 - The Molecular Biology of Translation
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 9, Problem B.5
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.
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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.
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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.
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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.
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Related Practice
Textbook Question
Answer the following questions for autosomal conditions such as PKU.
Parents who are each heterozygous carriers for a recessive mutant allele have a child who does not have the condition. What is the chance this child is a heterozygous carrier of the condition?
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Textbook Question
Answer the following questions for autosomal conditions such as PKU.
If the first child of parents who are both heterozygous carriers of a recessive mutant allele is homozygous recessive, what is the chance the second child of the couple will be homozygous recessive? What is the chance the second child will be a heterozygous carrier of the recessive mutation?
403
views