Phenylalanine Oleg A. Shchelochkov Charles P. Venditti Keywords phenylalanine phenylketonuria PKU hyperphenylalaninemia phenylalanine hydroxylase tetrahydrobiopterin BH4 Phenylalanine is an essential amino acid. Dietary phenylalanine not utilized for protein synthesis is normally degraded by way of the tyrosine pathway ( Fig. 103.1 ).…
Many childhood conditions are caused by single-gene mutations that encode specific proteins. These mutations can change primary protein structure or the amount of protein synthesized. The function of a protein, whether it is an enzyme, receptor, transport vehicle, membrane component,…
Rare and novel disorders often present in childhood and represent a diagnostic challenge that can be addressed using advanced genetic techniques. In the United States, rare disorders are defined as those affecting <200,000 people (about 1 in 1,500 persons), but…
Pediatricians are asked to consider the possibility that certain conditions involve epigenetic mechanisms. The assumption is that epigenetic processes, generally defined as regulatory control of gene expression, are capable of overriding information encoded in the DNA sequence to increase or…
Common pediatric diseases are usually multifactorial. The combination of many genes and environmental factors contribute to a complex sequence of events leading to disease. The complexity of the combination of contributing factors increases the challenge of finding genetic variants that…
Clinical cytogenetics is the study of chromosomes: their structure, function, inheritance, and abnormalities. Chromosome abnormalities are very common and occur in approximately 1–2% of live births, 5% of stillbirths, and 50% of early fetal losses in the 1st trimester of…
Family History and Pedigree Notation The family history remains the most important screening tool for pediatricians in identifying a patient's risk for developing a wide range of diseases, from multifactorial conditions such as diabetes and attention-deficit/hyperactivity disorder, to single-gene disorders…
The human genome has approximately 20,000 genes that encode the wide variety of proteins found in the human body. Reproductive or germline cells contain 1 copy (N) of this genetic complement and are haploid , whereas somatic (nongermline) cells contain…
Since the completion of the Human Genome Project, we have seen an unprecedented expansion in our understanding of how human health is impacted by variations in genomic sequence and epigenetic , non-sequence-based, changes that affect gene expression. This period has…
Genetic testing involves analyzing genetic material to obtain information related to a person's health status using chromosomal (cytogenetic) analysis (see Chapter 98 ) or DNA-based testing. Diagnostic Testing Diagnostic genetic testing helps explain a set of signs and symptoms of…