Chapter 3, Problem 1CS

Summary Introduction

To determine: The reason for the inability to detect PKU in amniocentesis.

Introduction: The given case study describes a couple who have given birth to a second child and are informed about their newborn daughter’s genetic screening tests. The genetic tests indicated abnormally high levels of amino acid phenylalanine in the blood. Phenylketonuria (PKU) also known as hyperphenylalaninemia. This occurs 1 in every 10,000 births. It is an autosomal recessive disorder implying that both the alleles of the patient are affected. When untreated, it can lead to intellectual disability, seizures, and hyperactivity.

Explanation of Solution

The disease PKU is caused due to the abnormal metabolism of the amino acid phenylalanine which is not identified during amniocentesis. This procedure can detect any abnormality in the genes of the fetus. The presence of extra or absence of the chromosomes or their genes can be detected using amniocentesis. However, in PKU, the chromosomes are intact. The genetic composition for the nucleotides coding for amino acid alone has been changed. This is not identified using this method.

Thus, the disease PKU could not be detected in amniocentesis as the disease results in alteration of amino acid balance and not in the chromosomal pattern.

Summary Introduction

To determine: The disorders detected by amniocentesis.

Introduction: Phenylketonuria is a recessive disorder that mainly affects the Caucasian and the Asian populations. This disease is marked by increased levels of phenylalanine in the blood. It can result in intellectual disability and other physiological problems.

Explanation of Solution

Amniocentesis can detect various disorders that are marked by chromosomal abnormalities like increase or decrease in the number of part of chromosomes. This detection can be used to make an informed decision about the developmental needs of the fetus, and the required genetic screening and treatment.

The most common diseases detected by amniocentesis are Down syndrome or Trisomy of 21, neural tube defects, cystic fibrosis, Turner syndrome, Klinefelter syndrome, trisomy of 18, and many more.

Thus, the diseases detected by amniocentesis are the ones that alter the chromosomal number in an individual.