Zusammenfassung der Ressource
PKU
- Genotype
- Alleles: Different forms of a gene.
- Normal/wildtype allele
- Defective/mutant/disease-causing allele
- Individuals with 2 normal alleles are phenotypically normal
- Produce lots of phenylalanine hydroxylase
- Individuals with 1 normal allele and 1 defective allele are phenotypically normal
- Produce adequate amounts of phenylalanine hydroxylase
- Individuals with two defective alleles have PKU
- Do not produce a functional phenylalanine hydroxylase
- Recessive condition because the affected individual must have two copies of the defective
allele
- Chromosomes
- Humans have 46 chromosomes
- 2 of each - chromosome number (1-22) and XX or XY
- Chromosomes 1-22 are called autosomes
- X and Y chromosomes are called sex chromosomes
- Y chromosome has gene for males
- The gene that encodes phenylalanine
hydroxylase is found on chromosome
12
- PKU is an autosomal recessive disease
- How common is PKU?
- Northern Europe: 1 in 10,000
- Ireland: 1 in 4,500
- U.S. Whites - 1 in 8,000
- U.S. Blacks: 1 in 50,000
- Incidence of PKU is
approximately 1 in 10,000 births
in Ontario
- Newborn Screening
- Babies tested shortly after birth for PKU
- The Guthrie Test
- Blood sample taken
- Blood is placed on a plate
with bacteria that need
phenylalanine to grow
- A positive test that shows a halo of
growing bacteria surrounding spots with
excess phenylalanine
- Mass spectrometry is now
used to detect elevated levels
of phenylalanine in a
newborn's blood
- Dietary management of PKU
- Reduce intake of phenylalanine
- Diet includes protein supplements in
which phenylalanine is reduced
- Special formula for infants and toddlers
- Protein mixes for children and adults
- Avoid aspartame
- PKU and Pregnancy
- Women with PKU must resume the
special diet during pregnancy
- Excess phenylalanine in the blood can
cross the placenta and damage the foetus